Mast cell activation syndrome resource page

This post was last updated on July 13, 2024.

mast cell activation syndrome

The following is a long summary of my research notes and some self-experimentation that I engaged in as I waited for an appointment with a mast cell specialist, as well as updates from that appointment. It an aggregate of my own digging and learning, shared for information and education purposes.

Table of Contents


The following are discussed in more detail on this (long!) page. A summary of some main points:

Mast cells exist all over the body, and symptoms can therefore occur all over the body. I am celiac, but my MCAS does not manifest with many GI symptoms, perhaps because I’ve long had that aspect under control. Other patients I know are constantly in the bathroom. It will differ person-to-person, and one patient may have anaphylaxis that differs from another patient’s symptoms and reactions.– For patients with “wonky tissue” aka those with Ehlers-Danlos Syndrome or another connective tissue disorder, significant periods of mast cell dysfunction may result in visible changes to skin. With abnormal mast cells and collagen synthesis, and with mast cells living in the body’s tissues, this seems to be the most common comorbidity in the patient cohort. In noting “significant periods”, I include clearing viruses like EBV, SARS-Cov-2 and dengue fever, among others.

– With over 1000 mediators released by mast cells, affecting 200 + receptors in the body, there’s much to look at. However, tests yet to be developed to measure many of them. Each patient’s symptoms will be different, usually with some overlap. Histamine is often discussed in literature or blog posts online, but that is insufficient. There are far, far more mediators released than just histamine, and it’s important to not ignore the others.

– This also means that triggers can be different for each patient, be it environmental triggers or food-related triggers. These include excipient ingredients (fillers) in pills, radiological dyes and even procedures that cause pain. It is important to premedicate for procedures and surgeries. See the recommendations under “triggers”, below. Some people even react to their own sweat (I know, right?), or to vibrations, or to sunlight. One common trigger for most patients is situations of trauma and stress. The many other triggers that exist will vary person to person.

A mast cell flare is not the same as a “true” allergy. True allergies can be identified with blood tests. Mast cell reactions vary based on someone’s baseline, and will not be identifiable in the same way. See the bucket analogy graphic, below.

– Many conditions are comorbid with mast cell disorders, some of which are set out in on this page.

Diagnosing mast cell conditions is not simple. Many practitioners falsely believe that a normal tryptase is indicative of no mast cell disorder. Patients sometimes get diagnoses (MS, lupus, anxiety, interstitial cystitis and more) that reflect one arm of mast cell problems, only to find out later that treating MCAS goes a long way to mitigating those (and other) symptoms.

– Given how patients differ with respect to triggers, it makes sense that treatment is also bioindividual. Baseline treatment for mast cell activation syndrome is usually an H1 and an H2 taken together, twice a day. This 12-hours-apart regimen is known by some experts as a “histamine blockade”. Finding the brand that works best for you will involve testing different brands methodically until landing on one your body likes. In addition, many patients benefit from natural mast cell stabilizers like quercetin, as set out below in the “naturally” section. Some also require prescription stabilizing medication, like ketotifen or sodium cromolyn. I have shared what worked for me thus far, but given how complex and varied the condition is, it does not favor a one-size fits all approach.

Treating mast cell activation syndrome with only natural products is a difficult ask for some patients. I find it problematic that some blogs or sites shame patients for using a combination of antihistamines and natural products. The reality is that while working with underlying causes is important, for many patients doing so will STILL require a stabilization beyond what natural products can do. I have heard from patients only using natural products who then have to add H1/H2 blockers, and feel shame about it. This is unacceptable. I have not met a complex patient who was “lazy” about their health; everyone wants to get better and is willing to work hard to get there. Using antihistamines does not mean a patient has “failed”, it means that their root cause is hard to come by (genetics, for some!), and science has yet to catch up with their body’s needs. I do think lifestyle changes including diet, neural retraining, EMDR, supplements, and more are critical. But uncontrolled inflammation is no good for anyone, and if you are a patient where natural options alone do not suffice, do not let anyone shame you for it. (For what it’s worth, many naturopathic and functional doctors also discuss the need for pharmaceuticals over and above natural stabilizers and treatment.)

– Speaking of the science: of the science right now, MCAS does not have a cure. It can only be carefully managed. There are some new receptor targets that look promising. And there are some cases where root causes are found, eg. some practitioners have found underlying immune deficiency where treating that helps condition mitigate the issue. Patients seem to think this means that the person is back to normal, so to speak. While I do hope the science evolves to find a way to put the genie back in the bottle, even in those cases anecdotally a baseline treatment is still required a lot of the time. But be wary of people (especially paid-courses!) that boast “curing MCAS”. For those without a full blown mast cell disorder, lifestyle changes like diet and supplements and more may resolve their issues. With MCAS and sister disorders, however, there is only management and temporary remission.

– Some mast cell experts are looking at the condition as an epigenetic, and not only a genetic disease, meaning that it would in principle be reversible with the right medication targeting the epigenome. There’s a paucity of research in this area for now, but it is an interesting avenue to keep an eye on, what an April 2022 paper called the “novel concept” of MCAD being rooted in an unnamed transgenerationally transmittable epigenetic disease.

– Many patients with anxiety have found that treating mast cell activation goes a low way toward lowering their baseline anxiety levels. This is not everyone, but specialists have documented cases where patients who previously had panic attacks, prolonged insomnia, and even a diagnosis of generalized anxiety disorder have watched those disappear with treatment for MCAS. In my case, I always had trouble sleeping and thought I had anxiety. Both of these problems went away now that I have my mast cells under more control.

– With Long Covid / PASC in the mix during the pandemic, some mast cell specialists are seeing an explosion of MCAS in that group of patients. I do hope the seeming correlation between Long Covid and mast cell-mediated hyperinflammation leads to more research that would benefit us all.

– And finally (long summary for a long page, I know), a newer condition called Hereditary Alpha Tryptasemia (HATs) is something patients with higher tryptase ought to look into. While MCAS testing is more complicated, HATs testing is a simple DNA test that any doctor—PCP/GP or specialist—can request via a company called Gene by Gene (see link below under diagnosis). HATs occurs where patients have inherited extra copies of the alpha tryptase gene (TPSAB1), and this leads to increased levels of tryptase protein detected in the blood, whether a reaction is happening or not. Per the research, the more copies one inherits, the higher the blood tryptase level. Unlike MCAS, this is easily documented and useful to rule in or out. While treatment is not too different, it will likely result in taking more seriously since testing is so straightforward.


For me, the first sign of these issues was actually in childhood. I had a cough that would itch my throat when trying to sleep, causing sleep disturbance from a young age. The cough went away when I hit puberty, but came back when I got sick on the trans-Mongolian trains en route to Ulaanbaatar. Then, following dengue fever in Vietnam, more hints: itchy skin when I exercised, itching when I ate certain foods like blue cheese, or drank red wine, and a first foray into seasonal allergies during first spring in Oaxaca, Mexico. They were so bad that my eyelashes fell out.

I had no idea what was going on, and only end up looking at mast cells as a potential cause after I sustained a spinal CSF leak following a lumbar puncture in 2017. I saw many leak patients dealing with very similar issues, read up on dengue and mast cells (who knew!) and then it all culminated in my going into anaphylaxis during my 4th blood and fibrin glue patch and needing an epinephrine jab on the table. I have been working on managing my ‘angry’ mast cells since that fibrin glue patch in early 2018.

For reference, prior to starting the regimen below, I had 24/7 searing/burning pain on my skin (spine, hands, feet, etc), adrenaline dumps at night that kept me up until 5am with my heart racing, I’d shake from cold exposure or cold drinks, low blood pressure, hives, gastro-intestinal distress, and anaphylaxis exposure to certain triggers. Since using the protocol I’ve shared here, those have all disappeared, save for occasional reactions to new foods or smells. The skin burning disappearing was especially a relief, as is my ability to sleep again.

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Mast cells are “sentinels” of the immune system, a type of white blood cell that helps control the immune processes in the body. They are called resident immune cells because they reside in tissues and not in our bloodstream. And they reside in tissues all over the body, from the connective tissue, to the endothelial cells, to the epithelial cells, and even in the brain.

Mast cells are immune system cells that live in the bone marrow and in body tissues, internal and external, such as the gastrointestinal tract, the lining of the airway, and the skin. Everyone has mast cells in their body, and they play many complex and critical roles in keeping us healthy. The positive roles that they play include protecting us from infection, and helping our body by participating in the inflammatory process. However, mast cells are also involved in allergic reactions, from the tiny swelling that appears after a mosquito bite to a life threatening, full-blown anaphylaxis.

-The Mastocytosis Society of the United States (TMS); Source.

They’re important – we need them! – but as with many conditions out there when they get out of balance, things go awry.

Dysfunction of mast cells can cause severe diseases, and can lead to a wide variety of problems and symptoms. Since the mast cells reside all over the body, those symptoms are often systemic. And since each of us has a different immune system, the symptoms and manifestations of mast cell disease varies across the patient population.

What is mast cell degranulation?

Mast cells are filled with tiny granules, as you can see in the screenshot of the video below. When they get “angry,” a destabilization process known as degranulation, they dump up close to 1000 different signalling chemicals—called mediators—into the bloodstream. Those mediators are inflammatory, and the degranulation process kicks up a cascade inflammation that can affect other workings in the body. Mast cells exist in organs and tissue throughout the body, and mediate allergic, immune, and inflammatory reactions.

We don’t want to eliminate the mast cell’s ability to degranulate. As the quote above illustrates, the degranulation response is part of the body’s natural defence when it senses invaders, and part of what helps keep us safe and healthy.

The problem is that in mast cell activation syndromes, that normal defence response goes off the rails. The mast cells get riled up* and mount a defence for innocuous things that would not otherwise be a threat. The immune system now thinks things that would not deserve an ATTACK! response for a ‘normal’ immune system now do.

resting mast cell vs an activated mast cell
Resting mast cell vs. an activated one. Source.

Essentially, the normal mast cell process is altered and the mast cells are sensitized and degranulate with exposure to a variety of triggers, including excipients in medication, stress, and more. I go into the types of triggers below.

*Yes, I am anthropomorphizing mast cells. I find it helpful to think of them as friends I’m trying to negotiate with.

Below is a short video showing what happens when mast cells degranulate:

And here’s an image, for those who don’t have the bandwidth for video:

Image of mast cells degranulating to show how they can affect the body
Mast cells degranulating. Image Credit: Sakurra / Shutterstock

Mast cell degranulation can lead to feelings of increased anxiety and other neuropsychiatric symptoms

Mast cell degranulation can also increase anxiety, via the release of meditators like histamine at high levels into the bloodstream. A Psychology Today article even called for examining patients for mast cell dysfunction when they present with anxiety, depression, or brain fog, noting:

When patients consult their primary care doctor with many seemingly random dramatic complaints affecting unrelated organ symptoms, which often feature prominent psychiatric symptoms, they are often thought to be suffering from a psychosomatic condition and told “its all in your head.” They may be sent home with a prescription for an antidepressant or anti-anxiety medication, which not only is experienced as invalidating but does not address the root cause of their symptoms. Identifying MCAS as the source of symptoms has important treatment implications and can speed recovery.

Furthermore, a 2017 case study entitled “Mast cell activation disorder masquerading as a nervous breakdown,” notes that a patient who presented with severe psychiatric symptoms was actually found to have MCAS, and his neuro-psych symptoms dissipated once the mast cells were stabilized. That same paper states that “although rare, some patients can present with minor neurocognitive disturbances as well as frank psychotic behaviors.”

An October 2023 study, Neuropsychiatric Manifestations of Mast Cell Activation Syndrome and Response to Mast-Cell-Directed Treatment: A Case Series, the authors wrote:

“We theorize that MCAS-associated neuropsychiatric disorders could be caused by abnormal MCs in the central and/or peripheral nervous system or indirectly by circulating MC mediators that lead to inflammation in the nervous system. MCs, known as immune and pro-inflammatory effector cells, are present in the meninges and are implicated in the pathophysiology of migraine via neuropeptide release, vasodilation, and plasma and protein extravasation, which can lead to MC degranulation. Since MCs release hundreds of various mediators, including histamines, tryptases, and leukotrienes, the degranulation of meningeal MCs contributes to the sensitization of trigeminal vascular afferent processing. This MC-mediated pathway is thought to be one of the mechanisms underlying migraine pain pathophysiology, and migraine is one of the most common comorbidities noted in patients with MCAS.”

In addition to the foregoing, the study also notes the presence of circulating autoantibodies, several types of which are also found in Long Covid, that may be affecting the brain and autonomic nervous system due to a mast cell-induced hyperpermeable blood brain barrier and/or an abnormally functioning blood–cerebrospinal fluid barrier. As someone with a spinal CSF leak, this made my ears perk up. The blood-cerebrospinal fluid barrier’s abnormal functions in the choroid plexus of the brain is seen in some Lupus patients with neuropsychiatric symptoms. The theory is that post-viral or general permeability of these barriers is part of why neuropsychiatric symptoms are so extensive.

In that 2023 study, each of the patients experienced significant improvements of neuropsychiatric and multisystemic symptoms after mast-cell-directed therapy. The study therefore concludes that in neuropsychiatric patients who have systemic symptoms and syndromes, it is important to consider the presence of an underlying or comorbid MCAS.

Anecdotally, several MCAS patients I’ve spoken with have said their anxiety levels plummeted once the mast cells were stabilized, including several who had a “feeling of doom” that accompanied extreme anxiety. For me, controlling mast cells help racing thoughts and/or adrenaline surges before bed; it turns out it wasn’t stress or anxiety after all.


All mast cell diseases are caused by the proliferation and accumulation of sensitized/altered mast cells or the inappropriate release of mast cell mediators, creating symptoms in multiple organ systems. There are a few main forms of mast cell diseases: mast cell activation syndrome, mastocytosis, and the newer Hereditary Alpha Tryptasemia Syndrome (HATs). Mastocytosis is further broken down into different subtypes.

Mast cell diseases can cause tremendous suffering and disability due to symptomatology from daily mast cell mediator release, and/or symptoms arising from infiltration and accumulation of mast cells in major organ systems. Although systemic mastocytosis is a rare disease, those suffering with MCAS have recently been increasingly recognized and diagnosed. As a result, patients with MCAS appear to represent a growing proportion of the mast cell disease patient population. It is important to note that the process of mast cell activation can occur in anyone, even without a mast cell disease, as well as in patients with both mastocytosis and MCAS.
– The Mastocytosis Society of the United States

MCAS, Mastocytosis, and Histamine Intolerance

The focus on this page is mast cell activation disorder (MCAS), which is when the mast cells are hyperactive and degranulate easily, and too frequently). An April 2020 study estimates that “this disease that could affect up to 17% of the population on a spectrum from very mild to debilitating symptoms. MCAS is often either misdiagnosed or the diagnosis is greatly delayed due to a lack of provider awareness.” MCAS is often a lifelong issue, like my glimmers from childhood, that gets fast-tracked by trauma, viruses, and more.

As noted above, there is also also mastocytosis, where a patient has too many mast cells and they are often also prone to easy degranulation. Mastocytosis, of which there are several varieties, is often confirmed with a bone marrow biopsy that looks for a KIT gene mutation. This is because more than 90% patients with mastocytosis possess mutations in the KIT gene, most of them in KIT D816V.

There are several different variants of mastocytosis, but most common are cutaneous mastocytosis, and systemic mastocytosis. Diagnosis for mastocytosis happens as follows:

  • Cutaneous mastocytosis is diagnosed by the presence of typical skin lesions and a positive skin biopsy demonstrating characteristic clusters of mast cells.
  • Systemic mastocytosis is diagnosed usually via bone marrow biopsy. The WHO has established criteria for diagnosing it, which includes a major criteria of a specific density of mast cells plus minor criteria that include a KIT D816V mutation, serum total tryptase, and more.

Then there is Histamine Intolerance, which my mast cell specialist believes it is essentially a milder case of MCAS. Other practitioners believe it may be rooted in microbiome or gut issues, or genetic issues that create a lack of DAO in the body, which is an enzyme that helps break down histamine. The DAO and HMT pathways are both implicated in histamine intolerance, and certain medications and foods can deplete DAO in the body as well.

Per expert Dr. Joneja, taking supplemental DAO and going on a low histamine diet can help these patients (see my recommendations in the “treating naturally” section below). If you believe that your issue is histamine intolerance and not MCAS, please see Dr. Joneja’s PDF primer about it here

That said, mast cell diseases are transcend histamine alone; with over 1000 mediators released by the mast cells, histamine is but one of them. For those where DAO and low histamine diets are insufficient, you may want to think about in-depth mast cell testing.

This image below from a January 2020 study “Mast Cells: Fascinating but Still Elusive after 140 Years from Their Discovery,” is also a helpful pictorial demonstration of the many conditions that can arise when the normal mast cell process gets dysfunctional.

Some of the many conditions that involve mast cells, such as asthma, cancer, celiac disease, MS, and more.
This figure shows the wide variety of conditions where mast cells have been implicated.

From the study, with full citations here:

This figure schematically illustrates the wide spectrum of pathophysiological conditions in which mast cells and their mediators have been implicated. For several decades mast cells were considered to play mainly proinflammatory roles in several allergic disorders, such as bronchial asthma, allergic rhinitis, urticaria, food allergy, anaphylaxis, atopic dermatitis, and angioedema.

In my case, even changes to my thyroid labs—my TSH, Free t4 and Free t3 were all out of range—were attributable to my mast cell dysfunction. Once I stabilized my mast cells with ketotifen, the labs went back to normal within months. I later learned that scientists are researching the possibility that histamine may be the connector of a novel neuroendocrine pathway linking the thyroid with mast cells.

During the last years, it became evident that mast cells represent an important cell during bacterial, fungal, viral, and helminth infections. Elegant studies have demonstrated that mast cell-derived mediators can play protective roles against several venoms. Mast cells and their mediators can be involved in several aspects of tumor initiation and growth, presumably through the production of several angiogenic and lymphangiogenic factors. Systemic mastocytosis is a clonal disease associated with a somatic gain-of-function KIT mutation. Mast cells, strategically located in different sections of the human heart and atherosclerotic plaque, are involved in different phases of atherosclerosis and myocardial infarction. These cells can be involved in several autoimmune disorders, such as rheumatoid arthritis, coeliac disease, multiple sclerosis, and bullous dermatoses.

Mast cell–nerve communications are involved in stress, pain, pruritus, and in inflammatory bowel diseases.

Mast Cells and Nerves

There’s a lot of science discussing the association between mast cells and nerves in most tissues, including studies that suggest the mast cells are constantly providing information to the nervous system. Mast cells are also widely distributed in both connective tissue and mucosal surfaces, and interact with their environment locally in very different ways. They’ve got a load of different functions, too – they’re thought to play a major role in resistance to infection, and are involved in inflammation and the tissue repair that follows initial inflammation during an injury. They also are involved in hair follicles!

And that’s just the tip of the iceberg. They’re involved in so much of the body’s processes that patients go to different specialists with seemingly no commonalities within their symptom profile—only to later find out that the mast cells, located all over the body, are the culprit.

Mast cells are capable of the synthesis of a large number of pro- and anti-inflammatory mediators, including cytokines, growth factors and products of arachidonic acid metabolism. Pre-stored mediators, such as histamine, serine proteases, proteoglycans, sulphatases, and tumour necrosis factor (TNF), are released within minutes after degranulation of the cell.”

Full study/explanation of mediators in Significance of Conversation between Mast Cells and Nerves.


One of the challenges in having a systemic, complex disease is how you communicate your needs and/or explain the condition to family and friends.

Most people are familiar with traditional allergies, which are described below and consistent of an allergen that is a constant trigger, often worsening each time you are exposed. Given the systemic aspect of mast cell disease, it’s less binary and less “I’m going to die if I come into contact with this thing—though there are mast cell patients who also have IgE allergies. For example, I am allergic to bee venom and have an EpiPen for it. This is a non-changing allergy that is very severe in its anaphylaxis and I have to be vigilant.

Unlike IgE allergies, living with MCAS feels like using an abacus all day long. Can you eat this thing? Well, how stressed are you right now. How much pollen is in the air? How many mast cell stabilizers are you taking?

It’s a lot of spinning plates to keep track of, but once you stop trying to make binary rules and let yourself explore the triggers you may have with curiosity instead of resentment, it becomes a lot easier to keep track of. Some things may always cause a reaction, but others may be only something you react to in tandem with how full your “bucket” is.

I highly, highly recommend getting a notebook to keep track of what you eat, supplements or medication you’re taking, what you’ve changed in your environment, and your symptoms to better allow you to narrow down on what your specific triggers are.

The “Bucket Analogy” in Mast Cell Activation Syndrome

With mast cell activation syndrome, exposure to triggers leads to reactions all over my body—sometimes culminating in anaphylaxis—but the severity of the reaction depends on a variety of factors all funneling into my immune system.

Unlike with traditional allergies, there are times that exposure to mast cell triggers as slightly less impactful than others. It all depends on the amount of water in my “bucket”. Once the water in the bucket overlflows, I stay in a prolonged mast cell flare. So my goal is to keep the water as low as possible, to prevent that from happening.

Here’s what I find raises and lowers the water for me in my “mast cell bucket“:

managing mast cell activation syndrome: triggers and support

Sample script for friends and family

Here’s how I use the bucket analogy to describe what’s going on:

“Imagine a bucket where many things cause water to flow into it. Most people have a drain that works and is fully open in it. I have two problems: my drain is pretty clogged up, and I have a lot of water flowing into the bucket. When the bucket is super full, even a drop of extra water will cause the bucket to overflow.

Overflow can be gastro symptoms, itching, nausea, bone pain, [INSERT YOUR SYMPTOMS] and much more.

So my goal is to keep my water levels as low as possible. To do that, I go on a low histamine diet (helps less water flow into my bucket), I take mast cell stabilizers and antihistamines (which do the same), take DAO (an enzyme that breaks down histamine) with meals, which helps clear the drain a little bit.

But it takes constant calibration and also a calculus to try and make sure I keep the water low, and the drain as clear as possible. Keeping the bucket from overflowing also requires that I stay aware of so many little things that may go into the bucket. Environmental triggers, food, smells, and a lot of other little things that most people don’t need to pay attention to. I never needed to care about these things, but now a “little” exposure can lead to me being very sick for days.

So while I may appear over-cautious, or fussy, in reality it is what I need to do in order to stay as healthy as possible with this complicated condition.


What are the Symptoms of Mast Cell Activation Syndrome?

Because mast cells exist in so much of the body’s tissues and systems, when they degranulate a large range of symptoms throughout the body may occur.

  • Flushing of the face, neck, and chest Itching, +/- rash
  • Hives, skin rashes – see TMS’ “visual guide to skin lesions” for more, here.
  • Angioedema (swelling)
  • Nasal itching and congestion
  • Wheezing and shortness of breath
  • Throat itching and swelling
  • Headaches
  • Alcohol-withdrawal headaches specifically, via a mast cell receptor MrgprB2. No other cells have this receptor.
  • Brain fog and cognitive dysfunction, accompanied with anxiety or depression
  • Diarrhea, nausea, vomiting, abdominal pain, bloating, gastroesophageal reflux disease (GERD)
  • Bone/muscle pain, osteosclerosis, osteopenia, osteoporosis
  • Light-headedness, syncope/fainting
  • Rapid heart rate, chest pain
  • Low blood pressure, high blood pressure at the start of a reaction
  • of a reaction, blood pressure instability
  • Uterine cramps or bleeding
  • Tinnitus / ear ringing (see the “other conditions” section below as well)
  • Dermatographism (can write on your skin leaving a red welt where you traced something with fingernail or blunt object; more here.)
  • Edema (fluid accumulation in different parts of body)
  • Decreased wound healing
  • Interstitial cystitis
  • Deterioration in dentin and teeth
  • Often liver enzymes that are wonky (High bilirubin, elevated liver enzymes, and high cholesterol)
  • Brain fog
  • Coagulation issues and blood disorders (Clots, deep vein thrombosis, easy bruising, heavy periods, nosebleeds and/or cuts that won’t seal up easily)
mast cell activation symptoms and effects in the body: a chart you can use to help parse through what's going on in your body.
Click here to download this chart.

Possible effects of different mast cell mediators on the body, when mast cells degranulate

Histamine: Flushing, itching, diarrhea, hypotension, panic attacks/anxiety
Leukotrienes: Shortness of breath
Prostaglandins: Flushing, bone pain, brain fog, cramping
Tryptase: Osteoporosis, skin lesions
Interleukins: Fatigue, weight loss, enlarged lymph nodes
Heparin: Osteoporosis, problems with clotting/ bleeding
Tumor Necrosis Factor-α: Fatigue, headaches, body aches

Symptoms of Mast Cell Activation Disorder by Area of the Body

Some readers find it helpful to think of symptom clusters by area of the body, which can also make it easier to sequester symptom clusters by medical specialty. I will say that in my experience, few practitioners have been willing to explore mast cells as a cause for my symptoms. The only times that they’ve been considered is when labs were normal and my symptoms disappeared once I increased a mast cell stabilizer.

Still, the disease is systemic and it can be helpful to examine symptoms by area. When I note symptoms I get, it refers to times when my mast cells are not under control. These symptoms go away when things are stable for me.

Heart: Patients report palpitations, tachycardia, lightheadedness, out of breath feeling when active, chest pressure or pain, atherosclerosis, hypotension or hypotension, and more. Ventricular fibrillation, coronary artery disease, Kounis Syndrome and cardiac arrest can also occur in mast cell patients due to excessive activation of the mast cells. Tree pollen and snow mold combined led to heart symptoms that were significant enough to warrant an ER visit. All symptoms resolved once I increased my ketotifen (mast cell stabilizer) dose. I never had seasonal allergies as an adult, until these last few years. Their impact has been more and more aggressive each year.

About Kounis Syndrome, Lisa Klimas from Mast Attack writes:

Kounis Syndrome is an acute coronary syndrome provoked by mast cell mediator release. In one series, ten mast cell patients (5 MCAS, 3 MMAS, 2 ISM) suffered acute coronary syndromes.  These patients reported “oppressive” chest pain of the type commonly seen in ischemic cardiac events.  The triggers for these events were diverse: venom immunotherapy, mepivacaine, exercise, penicillin, general anesthesia, wasp sting, metamizole and moxifloxacin.  In seven patients, the echocardiogram was normal.  In the remaining, left ventricular hypertrophy, anteroseptal hypokinesia, medioapical hypokinesia, inferoseptal akinesis, lateral apical akinesia and left ventricular ejection fraction of 40% were found on echo. Only six patients had elevation of troponin, a test commonly used to diagnose heart attack and acute coronary syndromes.

GI System: Reported symptoms include abdominal pain, bloating after eating, nausea, constipation or diarrhea (or, as a friend says of her issues: the constant roller coaster between the two), gastroparesis, heartburn, irritable bowel syndrome. [Ref]

Skin: Skin writing (dermatographism – my skin “lights up like a Christmas tree”, said my mast cell doctor), different rashes or red or brown spots that differ from the skin lesions in cutaneous mastocytosis, flushing (on the face and generally), stretch marks on the trunk or armpits, delayed wound healing (an issue for my spinal CSF leak!), ridges on the nails (also common in connective tissue disorders), hair loss, easy bruising, and itching. [See: “A Review of the Dermatologic Symptoms of Idiopathic Mast Cell Activation Syndrome”, here.]

Eyes, ear, nose, and throat: “Filmy” eyes are common, as well as irritation that is found in allergies (burning in the eyeballs), as well as sensitivity to bright lights, sun, and difficulties focusing vision. I get tics where my eyelids spasm when my mast cells are not well controlled. Tinnitus is very common (ringing in the ears), as well as sound sensitivity and occasionally reduction in hearing, mouth ulcers or canker sores (I get these frequently), burning pain on the tongue and mouth, geographic tongue, white patches on the tongue, problems with teeth and gums (patients report “crumbling teeth”, frequent cavities, and bleeding gums even though they take good care of their teeth and don’t eat much sugar), sore throat / red throat (I get this, alongside a hoarseness in my voice, especially upon waking when my mast cells are not controlled), post-nasal drip, sinus congestion.[More, via MastAttack]

Lungs/Respiratory: Pain or pressure in the respiratory tract, sporadic wheezing or coughing, difficulty breathing, and as with Ehlers-Danlos Syndrome, obstructive sleep apnea is common. Mast cells also contribute to pulonary fibrosis, and this is an area of study presently.

Lymph nodes/Lymphatic: Enlarged lymph nodes, for me usually armpit or neck. Excessive mast cell activation can lead to lymphatic permeability and vascular remodeling, as well as immune cell trafficking through the lymphatic vessels, making the cross-interaction between mast cells and other areas of the body a topic of study presently especially as it relates to cancer. [See “Emerging Roles of Mast Cells in the Regulation of Lymphatic Immuno-Physiology”, here.]

Urinary and Gynecological: I hear a lot about uro-gyn symptoms from readers, and the symptoms can be very uncomfortable. Symptoms include increased urinary frequency, incomplete urination, flank pain/burning, “feeling like I have a UTI” (painful peeing, burning in the genital tract when not urinating, and more)— but testing is negative, and symptoms ebb when mast cell medication is taken. Interstitial cystitis diagnoses are common. Genital tract symptoms are less common in men, and in women include vulvodynia, vaginitis, and/or itching and redness (readers thought they had a yeast infection or bacterial vaginosis, but it went away with mast cell treatment), painful intercourse, and bleeding during or after intercourse. [See here and here for urinary issues; here for gynecological issues, and with more on mast cells affecting pregnancy and postpartum: here, with the full study here.]

Neurologic and Psychiatric : I remember reading a case study where a doctor reported a patient who said their “panic attacks went away when I started my antihistamines”. This was early on in my mast cell journey, and since then I am constantly amazed at how much mast cell degranulation affects mood, sleep, and more. Neurologic symptoms include headache (often around temples; a “helmet” headache), dizziness, tingling, changing colour in hands and feet (for me, red and blue), burning in extremities, frequent nighttime waking but also inability to fall asleep, myoclonic jerks (jerking away when falling asleep), night terrors, and a few of you write in to also report sleep paralysis. In addition, psychiatric symptoms that have include anxiety (“physiological anxiety” is how some readers described it), panic attacks, depression, “histamine rage” aka irrational anger, brain fog, word finding problems and other cognitive dysfunction, [See here, with the full text of the study here, and a writeup from MastAttack here. Please also see the section on small fiber neuropathy, below.]

Blood sugar, diabetes: : high glucose levels, big fluctuations in glucose levels, diabetes mellitus, and more. Histamine affects insulin production, but the range of instability in patients using continuous blood glucose monitors is significant, so I hope we get more data as to why this happens, soon. [See here, here, and here (“observations from animal and human studies have suggested beneficial effects of treating diabetic patients with MC stabilizers“—but it’s not one size fits all)]

Cholesterol : It is common to have high cholesterol with mast cell activation syndrome. Mast cells are also involved in plaque (cholesterol) buildup in arteries, as noted in the heart section. [See here, here (includes liver abnormalities as well), here (includes metabolic issues as well).

Immune system generally : Lots and lots of allergies (not always IgE allergies) and sensitivities to the environment (for me, a new pollen, scents, and fragrances issue), slow healing from colds or infections, and often the presence of autoimmune conditions/diseases.

What are Triggers for Mast Cell Activation?

Triggers for mast cell degranulation are all across the map, from food to activity to environmental exposure and trauma. It’s difficult to imagine just how such disparate and seemingly innocuous things (vibration?!) can degranulate mast cells, but here we are.

The list below is cobbled together from the The Mastocytosis Society, the Canadian Mastocytosis Society, and blogs from around the web:

  • Intense exercise
  • Heat, cold or sudden temperature changes
  • Sun/sunlight
  • Fatigue
  • Stress, trauma, loss, emotional pain, family problems
  • Physical triggers, including pain, accidents, dental procedures, radiological dyes, surgeries, and other medical procedures. Both the Canadian and American Mastocytosis Societies recommend premedicating before any such procedures or dyes are administered. Radiation can also trigger mast cell issues. I had no problems with MRIs previously, but now have to premedicate even for non contrast MRIs. For medical procedures, radiological procedures, dental surgeries, and more see this 2023 PDF guide to bring to the hospital with you that discusses mast cell disorders, plus stages of anaphylaxis and triggers.)
  • Environmental (weather changes, pollution, pollen, pet dander, mold, gas leaks)
  • Food or beverages higher in histamine.See diet lists below under TREATING MCAS for more details. A big problem for people trying to get well is that many of the “no” list for histamine is actually recommended heavily for autoimmune diets – eg. fermented foods/natural probiotics, spinach, etc which will make MCAS symptoms worse for many patients.
    • Yeast
    • Alcohol
    • Dairy (especially fermented dairy like kefir, blue cheeses, or aged dairy like Parmesan cheese)
    • Gluten
    • Fermented foods (especially sauerkraut, kombucha, miso, kimchi, fish sauce, and soy sauce – anything that gives food a wonderful umami taste, basically)
    • Cured and smoked meats and fish
    • Shellfish
    • Citrus fruits
    • Vinegars
    • Canned and processed foods (canned products tend to have higher levels of histamine than fresh ones).
    • Overripe fruit and vegetables
    • Leftovers (I can tolerate dinner food the next day at lunch but that’s it. Usually, I will just freeze it right away and defrost to eat, so it stops the aging/histamine degradation process.
    • Berries, especially strawberries
    • Spinach
    • Chocolate other than pure dark chocolate
    • Tomatoes
    • Some food additives (see here for more)
  • A surprising amount of medications. The ‘avoid’ list includes some of the below. A longer list is here, and here. The latter list also includes medication that may work to calm mast cells.
    • Angiotensin converting enzyme inhibitors (ACE inhibitors) used to treat high blood pressure/hypertension can also increase bradykinin levels and therefore stimulates activation in mast cells
    • Amphetamines
    • Aspirin
    • Beta Blockers – many readers and studies note that beta blockers (for tachycardia, POTS, and more) can raise the floor on mast cell issues, making mast cells more likely to degranulate. This in turn can cause issues if a patient also needs epinephrine during anaphylaxis.
    • Dextromethorphan (cough suppressant)
    • Dipyridamole (Persantine)
    • Fungal infection drugs
    • Local anesthetics: some local anesthetics like benzocaine, tetracaine, and chloroprocaine, can trigger mast cell activation. Lidocaine or Carbocaine seem the best tolerated, but ask if there are preservative-free versions available.
    • Neuromuscular blocking agents (all):eg. Dexamethonium, Gallamine triethiodide
    • NSAIDs (Non-steroidal anti-inflammatories: Advil,Motrin,etc) – these can sometimes help patients, but in many they cause excess degranulation. You’ll have to figure out which category you fall into.
    • Most opiates (Codeine, Morphine, Percocet/Oxycodone, etc.) – from what I’ve read, fentanyl, Dilaudid, and occasionally Tramadol are best tolerated.
    • Thiamine hydrochloride (A form of vitamin B1)
    • Tolazoline hydrochloride
    • Trimethaphan and Trimethaphan
    • Vancomycin, often used with C. Difficile
  • Contrast dyes used in MRIs, CTs etc, whether iodine contrast agents or gadolinium. Some patients report gadolinium to be better tolerated, but others say it makes them feel sicker.
  • Mechanical irritation (rubbing/chafing) or friction
  • Vibration (for me, this included the MRI machine! I got a 3T MRI and had to take extra antihistamines as my body was jerking/moving despite my trying to stay still. This has never happened before 2020, and I don’t fear / have any issues with MRIs. It took me by surprise.)
  • Natural odours (strong natural scents like essential oils, environmental smells)
  • Strong odours (cleaning products, for example, or perfumes)
  • Infections (viral, bacterial or fungal infections can make MCAS worse and should be addressed carefully with help of your doctor – see below for how that works, including the image I included)
  • Venom (bees, wasps, spiders, snakes, etc.)
  • Diesel fuel (smell)

Viruses like Covid and dengue fever and EBV can sometimes lead to mast cell problems

Mast cells are involved in the body’s normal efforts to clear a virus, but prolonged infection or interaction with other aspects of the immune system can cause sustained mast cell problems, including with COVID-19 (see below).

For example, what kicked everything off for me as an adult was getting dengue fever from a mosquito on my travels. There are quite a few studies looking at the role of mast cells in dengue infections, including one that notes:

Immune cells called mast cells can hinder rather than help the body’s response to dengue virus, which suggests that mast cell products could be used as biomarkers to identify severe forms of the disease.

this image shows how viruses like dengue fever (and other virus) can affect mast cells and create a state of degranulation and vascular leakage--and how mast cell stabilizers like cromolyn and ketotifen can help.
“The response of mast cells to dengue virus can be beneficial or detrimental. When a mosquito injects dengue virus (brown hexagons) into the skin, the viruses are detected by specific antibodies (green) or unidentified receptors (blue) on the surface of resting (i.e., non-activated) mast cells. These can then trigger an anti-viral response (left) by releasing the contents of their granules (degranulation) and by upregulating intracellular anti-viral molecules (RIG-I and MDA5). The activated mast cells also secrete signaling molecules called chemokines, which recruit other immune cells including natural killer cells (NK), natural killer T cells (NKT) and T cells, which help to clear the virus. However, if local control mechanisms fail, the virus will enter the bloodstream and be carried to other organs (right). This activates the mast cells in these organs so that they undergo degranulation, releasing ready-made proteases such as chymase and tryptase, and synthesizing inflammatory mediators (leukotrienes and vascular endothelial cell growth factor [VEGF]). These increase the permeability of capillaries, leading to vascular leakage. Mast cells in these organs can also be activated by endogenous inflammatory mediators (such as C3a and C5a) that help the body to remove pathogens. Blocking mast cells (or their mediators) with drugs such as cromolyn, ketotifen and montelukast reduces pathogenic vascular leakage, but might also hamper viral clearance. Anti-mast cell therapy could thus be a double-edged sword.”

As the caption to the (ADORABLE) image notes, mast cells can be a double-edged sword in viruses, because we want them to do their job and clear out a virus, but when they are dysfunctional, they overdo it. And in non-MCAS patients, trying to tamp down on the response may, the study notes, prevent them from doing their job in clearing the virus altogether.

Studies relating to influenza also note that tamping down on mast cell activation can be beneficial. A study “Mast Cell-Induced Lung Injury in Mice Infected with H5N1 Influenza Virus” in mice notes,

A combination of ketotifen and the neuraminidase inhibitor oseltamivir protected 100% of the mice from death postinfection. In conclusion, our data suggest that mast cells play a crucial role in the early stages of H5N1 influenza virus infection and provide a new approach to combat highly pathogenic influenza virus infection.

So, all this to say: if you have a virus like Covid, dengue fever, influenza, and more, this too can be a trigger to activate mast cells. If you are genetically pre-disposed to mast cell problems, this may complicated your recovery. And treating mast cell activation can thus potentially mitigate severity of viruses, though we wouldn’t want to overshoot (at least in dengue).

In 2023, the American Centers for Disease Control (CDC) updated their post-viral illness page to list out viruses that can lead to long-term symptoms in the body, and included Covid, dengue fever, and EBV as some of the viruses known to do so.


As I wrote above, diagnosis of mast cell activation syndrome (or a sister disorder like mastocytosis or HATs) is often delayed due to lack of awareness about the nature of the condition and/or some practitioners testing only a narrow selection of meditators or only testing igE allergies.

In addition, the lab tests required to diagnose MCAS must be handled with great care and kept chilled. Specimens for urine testing also need to be kept cold at all times. The result is that several rounds of testing may be needed to confirm the lab results–which can be quite frustrating.

A differential diagnosis analysis is usually applied by the practitioner to rule out other inflammatory immune conditions or mimics of a mast cell disorder. Symptoms are so bio-individual, too, that it’s a lot harder to pin down a diagnosis than (say) a condition where it’s a simple gene test.  The labs below test for some mast cell meditators to ascertain their ranges, but the experts have noted there are hundreds mediators released by the mast cells in total, but only a few have lab tests to measure them.

For those in Canada, doctors often don’t run (or can’t order) many mediator tests as they are expensive and not covered by provincial healthcare. Some private mast cell practitioners will cover them, as will mast cell specialists in the United States.

How Can you Test for MCAS? (Labs, Urine, and DNA Tests)

Standard testing for MCAS includes both urine and serum (blood) tests. It can sometimes involve biopsies of the GI tract or colon. As stated earlier, samples can degrade really quickly at room temperature, and must be handled properly or else they will become corrupt. The mast cell doctor I saw said that laboratory or patient handling mistakes accounts for a lot of the false negative testing he sees, and he only works with specific labs that he knows he can trust to properly chill the samples.

Here were the tests the specialist order for me in order to assess whether or not I had mast cell activation syndrome:

Specific Blood Tests for MCAS

  • Histamine, blood
  • Histamine, plasma (chilled)
  • PGD2, plasma (chilled)
  • Comprehensive Metabolic Panel
  • Plasma prostaglandin D2 assay
  • PT + PTT
  • Heparin assay
  • Plasma heparin level Anti-Xa (anti-Xa for unfractionated heparin, chilled)
  • Tryptase, Serum
  • Chronic Urticaria Index
  • Anti-IgE antibodies
  • Chromogranin-A

Specific Urine tests for MCAS

  • Chilled Histamine, 24hr Urine
  • Histamine, Random Urine (then chilled)
  • Random urinary prostaglandin D2 (then chilled)
  • Chilled 24-hour urinary prostaglandin D2
  • Random urinary 2,3-dinor-11-beta-prostaglandin-F2-alpha (then chilled)
  • Chilled 24-hour urinary 2,3-dinor-11-beta-prostaglandin-F2-alpha
  • Random urinary N-methylhistamine (then chilled)
  • Chilled 24-hour urinary N-methylhistamine
  • Random urinary leukotriene E4 (then chilled)
  • Chilled 24-hour urinary leukotriene E4

DNA Tests

Notes about mast cell testing: read before testing!

  • You should not be asked to go off your antihistamines for testing. In Canada, some doctors do require this. In the United States, the main mast cell specialists absolutely do not. The consensus from mast cell experts is that antihistamines will not affect the results of serum and urine tests, since they only block the body’s receptors.
  • Some doctors do require you to get off mast cell stabilizers for testing. I went off quercetin, PEA, Vitamin E, and the other stabilizers listed above one week prior to testing, as well as anything that affected inflammation.
  • If you take NSAIDs like Advil, you are generally asked to stop 5 days prior to your testing.
  • If you take PPIs (proton pump inhibitors) you are generally asked to stop 5 days prior to your testing.
  • A note about tryptase: most mast cell patients with MCAS (not mastocytosis) test normally for tryptase, even during flares. This is why providers should be testing for multiple mediators.  However! As mentioned above, if your tryptase is elevated, you might want to also do a gene test for HATs, hereditary alpha tryptasemia syndrome, which is newer in the mast cell disorders world. It is an easier condition to rule in or out, because it requires a saliva gene panel that can be ordered online by Gene By Gene.
  • Tryptase is elevated in both mastocytosis (but not all cases of it) and in HATs. Since MCAS is a fairly new disease, some allergists or immunologists will test tryptase and, if it’s negative, say it’s not MCAS. That does not appear to be reflective of the data mast cell experts, even those who include tryptase in the requirements for diagnosis. Tryptase testing alone is not sufficient to rule out MCAS.
  • Among the mast cell experts, there are currently two ‘consensuses’ of diagnosis, with both of them accepted by the World Health Organization. One group consists of Drs. Afrin, Molderings, and more, here. The second group consists of Drs. Valent, Akin, and more, here. The second group that focuses more on tryptase, whereas Dr. Afrin’s group does not**. Both groups believe they are correct.
  • A note about IgG vs. IgE reactions: There’s often confusion about testing for food allergies or allergies using IgG and IgE testing. They are related to the functioning of mast cells, but not an accurate test for mast cell activation. So: yes, IgE allergens can lead to mast cell degranulation. But no, IgE testing (traditionally done by an allergist) is not used for diagnosis of MCAS. You can have no IgE allergies and still have MCAS. Conversely, many mast cell patients have issues with skin-writing, called dermatographism. I can easily write my name out on my skin and it’ll glow puffy and red for a long time. Skin IgE testing may just show reactions to the scratches and not necessarily the allergen; it’s not accurate for MCAS.
    • Mast cells have receptors for both IgE or IgG on them, and both types of antibodies can result in higher histamine levels or higher levels of other meditators, as well as triggering degranulation itself.
    • IgG reactions the calmer of the two, though they are still capable of producing anaphylaxis-like symptoms. These antibodies are common not only for pathogens we are affected by, but also food issues when we have issues with GI permeability (leaky gut and more).
    • IgE reactions, in contrast, are usually sharp and immediate — like when we are stung by something we are allergic to. It’s a fast-paced degranulation response by the sentinels of the immune system to try and protect from something significant. While not part of MCAS testing per se, they can be useful. It’s important to use IgG antigen testing if you are testing IgG, and then phase out those foods for several months to see if that makes a big difference, then try to reintroduce with nutritionist support.

**Drs. Afrin and Dempsey responded to comments about why tryptase should not be a reliable / gold standard marker for diagnosis mast cell activation syndrome, as follows, but the disagreement between experts continues:

In our combined clinical experience now across many thousands of MCAS patients, we (Dr. Dempsey and Dr. Afrin) have not seen a rise in tryptase to be a reliable marker of mast cell activation.  Again, a persistently elevated tryptase may be a reliable marker of an increased number of mast cells in a person, and a clear, brief spike in the tryptase level over some lower, stable baseline level of tryptase probably represents a brief flare of mast cell activation, but such a spike it is not a reliable marker of mast cell activation.  In fact, it appears that mast cells can become activated via so many different routes, releasing so many different mediators under different circumstances, that it is difficult to imagine how a spike (by any amount) in just one mast cell mediator could be a truly reliable marker of mast cell activation detectable in most activation events in most people.  We have even seen many patients whose tryptase levels have gone *down* during events of flagrant mast cell activation, such as anaphylaxis.  And we have seen that in patients whose symptoms are suggestive of mast cell activation, it almost always is the case that elevated levels of mast-cell-specific mediators other than tryptase can be found in the blood and/or urine.


The level of pain I was with the CSF leak and the (unknown to me at the time) mast cell dysfunction was debilitating. It got to a point where I simply sobbed in bed all day long. When my research led me to suspect a mast cell disorder, I implemented the following steps. They sharply reduced my pain levels while I waited for specialist testing.

** This is just what has worked for me so far and is not medical advice. **

FIRST, I identified triggers and removed them from my environment, like strongly-scented home cleaning products, non-natural cosmetic products or shampoos or face washes (see below for what brands I use), and more.
SECOND, I went on a strict low histamine diet for two weeks, removing things like alcohol, cold cuts and smoked/cured meats, canned fish, anything pickled or fermented, aged cheese, overripe produce, gluten (already done because I’m celiac), citrus fruit, spinach, yeast, soy, and tomatoes. I also stopped eating leftovers more than one day old, freezing anything I cooked after making it for future consumption. See the diet list below for the full list of items to remove. I then slowly added in some of the medium histamine foods.
THIRD, I added natural mast cell stabilizers like quercetin and PEA. See the protocol below for what I used.
FOURTH, additional lifestyle changes: a) cutting down on inflammatory foods and starting DAO, the enzyme listed below, 15 mins prior to eating higher-histamine meals, and b) reducing stress by implementing a meditation practice. Lowering stress can reduce levels of corticotropin hormone (CRH), a potent mast cell degranulator.
FIFTH, started experimenting with H1 antihistamines to see what helps. If an H1 didn’t work or make a big difference after two weeks, I stopped it and tried a different one. The standard dosing regimen for MCAS every 12 hours to create a “histamine blockade”, which is more often than H1s are usually taken for non-MCAS patients.
SIXTH, started experimenting with H2 antihistamines after I landed on “my” H1. As with H1s, these are meant to be dosed every 12 hours. I found ranitidine, at low doses, was the one that works best for me.
SEVENTH, to ensure some of my mast cell issues weren’t being fuelled by parasites or viruses, I did a stool test and specialist blood tests. I realize not everyone has access to this testing.

For each of these, it was important to go low and slow when onboarding new supplements or medication. Know that it’s very hard to know what is a material/substance you react to sometimes. I now have a long chart where I write in the stuff that works for me and its fillers, because the experts have made clear that excipients/fillers in medication are often what mast cell patients react to and not necessarily the medication itself. Here’s more on excipients in fillers: Recognition and Management of Medication Excipient Reactivity in Patients With Mast Cell Activation Syndrome, a 2019 review article.

Unfortunately, a 2024 study revealed that the main place patients go to look at excepients in North America, the DailyMed data base, is not as accurate as we thought. The study found that internal inconsistencies of excipients occured in 39% (!) of the formulations examined. So it’s best to go straight to the product monograph, if you can.

Briefly, some of the excipients readers have reported back on that give them trouble are:

  • magnesium stearate
  • polyethylene glycol
  • coatings on ‘extended release’ or ‘enteric’ pills, including shellac or dyes like FD&C red #5 or FD&C blue #2
  • povidone
  • alcohol

It wasn’t fun or easy, but with no access to knowledgeable medical care, it really helped me stay afloat until I could get to a mast cell specialist.


Eliminating Triggers

Reduction of triggers includes whatever triggers you from the long list I shared earlier. This means removing not only environmental triggers like shampoos and soaps, but also eating a lower histamine diet to potentially lower circulating levels of histamine in the body. While some doctors do not recommend a low histamine diet, I know that without sharply limiting the food I intake, I cannot stay on top of my reactions and symptoms.

(My lab testing also showed a very high level of circulating histamine–one of the highest my practitioner had seen; always an overachiever here, eh?)

Note that for many vibration is a trigger, so car rides, electric toothbrushes, and more can degranulate mast cells. For many essential oils are also too strong a scent and will cause symptoms.

Low Histamine Diet

Few mast cell patients I’ve spoken with eat a normal diet. As a former food/travel writer, this part is hard. I joke that I’m the worst food writer ever, but the truth is after wrapping my head around celiac disease 20 years ago, cutting things out strictly and systematically is not new to me. I just didn’t ever think I’d have to cut out so much!

Being on a low histamine diet can help reduce the overall burden on your body because it reduces the amount of histamine floating around. For non-MCAS patients, it can also sometimes help itching or asthma.

Some mast cell experts do not recommend going on a low histamine diet, and prefer to stick to medication and/or supplementation to control symptoms since histamine is but one mediator released by the mast cells. A 2021 study found that only 32% of the foods on many low histamine diet lists were truly high enough in histamine to be excluded. That said, at a 2022 conference on mast cell activation syndrome that I attended, several practitioners specializing in mast cell activation (including a gastroenterologist) noted that it’s a must.

It does appear that more doctors are seeing clinically that a low histamine diet does help symptoms and mood.

For me, that is certainly the case.

While my mast cells do release far more than histamine when they are agitated, I’ve seen big strides in my day to day baseline by removing certain foods from my diet.

What to eat or avoid on a low histamine diet

As I keep saying in this post: everyone’s body is different. That said, there are some commonalities where certain foods or food products are high in histamine, or histamine liberators, and the bulk of of the food lists recommend caution.

I made a chart to break it down more easily. The chart synthesizes the many food lists out there and includes the many years of community feedback from patients, as well as my own dietary changes:

low histamine diet for mcas - what i eat and what i avoid

Foods you can eat on a low histamine diet —

  • Many of us do great on meat that is fresh and unhung/not processed or aged. This includes lamb, chicken, veal, rabbit, turkey, and more. Best practices are to try and find products that are butchered and immediately frozen or vacuum sealed (preferably both). Ground meat is a tough one because it’s higher in histamine. I’ve managed fine on meat that is immediately frozen after being ground up. In general, you want to minimize exposure to air so meat that is vacuum sealed and fresh will be a safer bet than in loose packaging. Many products are vacuum sealed these days, so there is more to choose from.
  • Fish that has been flash frozen after being caught, and not pickled/brined. I can tolerate salmon sashimi if purchased from frozen (sushi grade).
  • Duck and quail eggs, though some people can tolerate chicken egg yolks.
  • Dairy that is safe for us includes regular (uncultured) butter, young cheeses like mozzarella, mild/young cheddar, coffee cream, fresh milk (though not everyone can tolerate), mascarpone and ricotta cheeses. Some people can also do cottage cheese or cream cheese; I’m not one of them.
  • Gluten free flour or grain options, like corn, rice flour, quinoa (high in oxalates though), amaranth, millet, oats, cassava, and more.
  • For nuts, I do well on the occasional almonds, brazil nuts, or cashew but I can tolerate macadamia nuts and chestnuts just fine. For seeds, sesame seeds in moderation, chia seeds, flax seeds or ground flax, hemp seeds, and occasionally pumpkin or sunflower seeds. I also frequently roast the seeds from any squash I cook, which are always so tasty!
  • Vegetables: basically, everything EXCEPT the things I list in the “avoid” section. In particular, people do great with lettuce, watercress, celery, artichokes, brussels sprouts, dandelion leaves, asparagus, bok choy (I eat this a lot!), fennel, cucumbers, zucchini, taro, red cabbage, and more. Some people do struggle with arugula, however. Also great are squashes like acorn and butternut squash.
  • Fruit: apples, apricots, blueberries (in smaller doses), cantaloupe, honeydew, Asian pear (Nashi pear), nectarines, peaches, persimmons, pomegranate, and lychee and longan are all low in histamine and delicious.
  • Most fresh herbs, including cilantro, oregano, sage, parsley, basil, allspice (I use it in the place of cinnamon, which is high histamine), and cardamom. Herbal teas are not fermented, and I love chamomile tea, stinging nettle tea, Rooibos, and more. Lemongrass also ok to season dishes!
  • I use maple syrup to sweeten baked goods, but tolerate Stevia and pasteurized (not raw) honey.

When cooking:

  • Many dietitians and mast cell posts will say to avoid cooking at high heats, including charring and/or BBQing. I do avoid these as much as I can, and boil instead of roast sometimes as boiling can lower histamine…but I have added in roasting and occasionally a BBQ because: joy. I have to adjust my “histamine bucket” (see below) for those days. Cooking oils that I use safely are coconut oil, hemp oil, olive oil, and ghee.
  • Leftovers are an issue, because the longer a food product sits there, the more histamine rises. This also includes overripe fruit or veggies.  

High histamine foods to avoid

  • Processed or cured meat, and beef: Meat that is smoked, cured (like bacon or charcuterie or sausages), or processed (sliced sandwich meat, hot dogs), and beef (as it is usually hung prior to being available for sale) are all high in histamine. If eating game meat, be sure to ask if it’s been aged or hung before it goes up for sale. Ground meat is also higher in histamine, and is best avoided unless it is ground and then immediately frozen, as per above.
  • Most fish, especially seafood (scallops, lobster, other shellfish), canned fish (tuna, salmon, anchovies), fish that has been smoked (mackerel, smoked salmon), and fish that has been sitting in the fridge / store for some time.
  • Some dairy: dairy that has been fermented (yoghurts, kefir, buttermilk, cultured butter), and aged cheeses like sharp cheddar, parmesan, gruyere, and more.
  • Chicken eggs, especially egg whites, are high in histamine. As mentioned above, some patients can tolerate chicken egg yolks. Personally, I do best with duck eggs.
  • Ferments: many diets that are espoused as “healthy” these days call for much spinach and ferments. These are histamine bombs. For ferments, we’re talking things like sauerkraut, kimchi, miso paste, coconut aminos, yeast, tamari and soy sauce, kombucha, and coconut milk / dairy alternative yoghurts.  It also includes breads that are fermented, like sourdough, and beer and cider. This also includes black and green tea, which sadly are fermented.
  • Pickled products: pickles! I love pickles. Sadly, these are now off limits and make me quite sick. Also add relishes, pickled onions, truffles, olives, and pickled carrots / cucumbers often found in Vietnamese food.
  • Some vegetables: the biggest culprits are spinach, eggplant, tomatoes, avocado, green beans, mushrooms, seaweed/algae, chili peppers of all varieties, and for many people pumpkin, broccoli, and Swiss chard can also cause issues.
  • Some fruit, especially dried fruit like dates, raisins, desiccated coconut, dried apples. As well as fresh fruits like bananas, grapes, strawberries, cherries, raspberries, and citrus fruits. I tolerate mango, but many do not. I can’t do grapes, but many others can. YMMV. Watermelon is also a hit or miss depending on the patient.
  • Most legumes and pulses, including soybeans (and edamame), chickpeas, lentils, black or red kidney beans, fava beans, broad beans, and more. Tofu also is a trigger for most patients.
  • Most nuts, seeds, and nut butters, especially peanuts, pistachios, walnuts, tahini, pine nuts.
  • Grains: as a celiac I’ve avoided wheat at all costs for a long time, but many patients do find a gluten free diet helps their symptoms. This is a personal choice, but either way there are many great non-wheat options around these days. Buckwheat is also higher in histamine, despite being gluten free.
  • Some spices, like black and white pepper, curry powders, anise, cinnamon, cloves, cocoa powder (also high in oxalate), mustard seed, nutmeg, chili powders, and hot paprika.
  • Oils: sesame oil, walnut oil, avocado oil.
  • Sweeteners: white sugar, brown sugar, raw honey, agave, malt syrup, coconut sugar, brown rice syrup.
  • Alcohol is high in histamine, especially fermented alcohol, but if you’re going to imbibe, the ‘safest’ option will usually be clear, distilled alcohols like vodkas or gins. I do find if I have white wine and use a “wine wand” I can have the occasional treat.

For me, a low histamine, medium oxalate diet seems to be the best baseline food plan, with occasional treats. I use a combination of the SIGHI list with Alison Vickery’s low histamine diet PDF:

  • Low Histamine: Swiss SIGHI lists. Elimination diet recommendations here. Food lists for histamine: a long PDF of graded histamine levels in foods/additives, etc here.
  • Low Histamine: Alison Vickery. Here is her DIET PDF. She uses a functional approach that combines naturopathic and allopathic medicine, and cites her sources fully. Of all the low histamine diet lists, this one has most matched how my body reacts to different foods.

Other diets that may help in stabilizing mast cells

In addition to low histamine, there are many patients who find extra relief using a low oxalate diet, especially for patients with pelvic inflammation or interstitial cystitis. A smaller subset of patients say they benefit from low FODMAP in addition to low histamine.

Some other “beyond low histamine” diet plans from around the web:

  • Some people with Ehlers Danlos variations or auto-immune issues such as Crohn’s or ulcerative colitis also have trouble digesting foods beyond the low histamine varieties. See this page about those additional restrictions, including a low histamine diet suggestion list for people who need to mindful of other categories.
  • These categories include lectins, oxalates, salicylates, sulfur, and FODMAPs, which — depending on the body — can affect MCAS as well. Note that if oxalates are an issue, higher-doses of Vitamin C will be a problem. It is important to keep track of data related to food and supplements to ensure you can pin down triggers.
  • Lectins are proteins found in some plants, and preliminary research suggests that they may activate mast cells also. For a low-lectin diet list, see here.
  • Oxalates are found in Vitamin C, which is an issue as high-dose vitamin C is helpful for mast cell stabilization, and for collagen synthesis. I have had to lower oxalate intake, which I did not realize was causing worse symptoms for me. There are many oxalate food lists out there, but you can start here.
  • FODMAPS: a low FODMAP diet can also reduce circulating histamine.

Apps that can help you manage low histamine and other diets

  • Baliza is a German company that has developed several apps that are useful for the low histamine diet, and both are updated as new data and studies come out:
    • Their app Food Intolerances is very thorough and allows you to sort by different food intolerances or allergies. Includes measurements for histamine, fructose, sorbitol, gluten, lactose, and FODMAPs.
      Apple here; Play store here.
    • Their app called OxiPur: measures foods by oxalate and soluble oxalate, searchable, sortable by food category, and includes some measurements related to oxalate content, like calcium in each food. Apple only, here.
  • Fig food scanner has a low FODMAP diet option, as well as other tweaks, and you can add foods you react to or ones you can’t tolerate. It lets you scan products from the stores, so it’s best for American readers as it’s based there. For Android here, or iOS here.

Supplements for Mast Cell Activation Syndrome

(Studies supporting why I take each of these products are below.)

  • Seeking Health DAO: DAO is an enzyme naturally produced in the body that helps break down histamine from food intake. Some people have genetic mutations that lower their DAO production, some people eating diets rich in products that lower DAO, and some people just need the extra DAO to help them mitigate the effects of high levels of circulating histamine. There are two products on the market that are trustworthy for DAO (in my opinion), and I use the Seeking Health version as the other one (Umbrellux) changed their formulation and it now does not work as well for me. This DAO is derived from porcine sources, and should be taken within 10-15 minutes of a meal high in histamine.
  • Vitamin C Nutribiotic Ascorbic Acid Powder (non-gmo, pharmaceutical grade) –
  • Vitamin C Nutribiotic Sodium Ascorbate (non-gmo, pharmaceutical grade). There is some evidence that sodium ascorbate also helps the extracellular matrix, so I include that in my supplements / total Vitamin C count.
  • Camu Camu, organic and freeze dried. My preferred vehicle for vitamin C. Note that if you have an oxalate issue, you will need to limit your vitamin C intake. This is unfortunate, since Vitamin C can help reduce histamine and also stabilize in other ways, but mast cell issues are truly an onion of catch-22s.
  • Non-GMO MicroIngredients Quercetin from Sephora Japonica buds If you prefer capsules, Jarrow Formulas Quercetin, Cardiovascular Support, 500 mg. Quercetin should be taken with fat to help it absorb. A more bioavailable version of Quercetin is the Thorne Quercetin Phytosome. The phytosome formulation, in this case bound with sunflower lecithin, helps the quercetin absorb better.
  • Zeolite: Functional medicine doctors believe that zeolite can help clear histamine from the body because it acts as a binder for the histamine itself. Zeolite is also used as a binder for metals for some.
  • Fisetin: mast cell stabilizer, also used for I use Life Extension or Doctor’s Best brands.
  • NasalChrom: Useful for seasonal-type allergies, food reactions that include nose running/itching in face. Sodium cromlyn is a mast cell stabilizer.
  • Zatidor eye drops: These are ketotifen fumarate, potent mast cell stabilizer – if you can’t access pills or compounded ketotifen, eye drops may help with oral symptoms considerably.
  • PEA: Palmitoylethanolamide, pure and from a reputable source. A company I trust and have used for years isVitalitus. When choosing a brand, it is important to make sure the supplement has been micronized to small diameters; this is the form the studies used that showed it was effective. PeaCure is the smallest diameter (they are ultra-micronized), and Vitalitus is micronized to less than 5 micrometers, and are a good second option. Their Soothamide PEA cream is also great, both for muscle and tendon pain, but also for burning skin with mast cell reactions. I also use it on my spinal CSF leak site.
  • Magnesium: there are several different types of magnesium available, and very opinionated views on which is best. I use Global Healing’s Oxi-Cleanse, which is magnesium oxide. I take this form of magnesium to help me stay regular. Unlike the instructions, though, I just take one per day of the magnesium oxide capsules. I pair this oxide with a capsule of either Vitamonk Quad Magnesium (it has magnesium orotate, glycinate chelate, taurate and di-magnesium malate), or a capsule of magnesium L-threonate (Magtein) from Doublewood.
  • The best Curcumin for mast cell patients that I’ve found is Thorne Soy Free Meriva. It has sunflower lecithin to help with bioavailabilty, and is soy-free. It is also made just from curcumin, so it does not have the higher-oxalate turmeric in it. The many other supplements in this category contain black pepper extract to help with bioavailability, but this is a mast cell degranulator. Meriva is a great option for those who want to try this.
  • Algonut PureLut Liposomal Luteolin (NOTE- not Lutein! Must be luteolin. Another option for luteolin, rutin, and quercetin is Neuroprotek. These are both is Dr. Theoharides supplements from his Algonot company, and profits fund further studies.)
  • Mirica® – Pea (Palmitoylethanolamide) and Luteolin – Natural Pain Relief – Made with OptiPEA® from The Netherlands, if you wanted to combine the two (Luteolin and PEA). I don’t do so, but it’s an option. The PEA is micronized, not ultra-micronized.
  • Amazing Herbs Premium Black Seed Oil, Organic and Cold Pressed.
  • Vital Nutrients Vitamin E 400 (with Mixed Tocopherols) (NOT soy free) OR, Healthy Origins Tocomin SupraBio (Tocotrienols) 50 mg –  if like me you don’t just want one of the tocopherol but rather tocotrienols too. (Soy free. 1 in AM and 1 in PM)

** Note that the links above for Amazon are affiliate links, where I get a small commission on the purchases.

My Current Protocol

This is just where I netted out and does not mean you should copy it wholesale. I am including it so people have an iduea of what I take.

  • 5mg H1 antihistamine twice a day, 10am and 10pm (levocetirizine). In Canada, this is not over the counter so I have had to get it compounded. It’s the best H1 for me, but each person is different. Also, many patients react to excipients in medication and thus require compounding regardless. The most popular compounding is with Avicel, a hypoallergenic filler, or with rice flour or baking soda. Check with a compounding pharmacy near you to learn about options. I may also be trial Rupatadine (Rupall in Canada), instead of levocetirizine, to see if it helps further. It is an H1 blocker, but also a PAF inhibitor, and my mast cell doctor thinks it may be more helpful for me.
  • 75mg, twice a day at the same time as my H1 antihistamine, of ab H2 antihistamine. I take, Ranitidine (MAR-Ranitidine is the brand in Canada), which is available by prescription here. Though this product was sold as Zantac and recalled in the United States, it is back on the market in Canada by prescription, with batch testing to ensure it is safe. The more common H2 antihistamine option now that ranitidine was pulled in the USA is famotidine (Pepsid is the most common brand name).
  • MicroIngredients pure powdered Quercetin – 1 scoop 500mg, 1x a day.
  • Quercetin phytosome – 2 capsules with dinner.
  • 1mg ketotifen – 1x with lunch, 1x at 4pm, and 1x at 8:15pm.
  • Meriva – 1 250mg capsule at lunch
  • Fisetin – 100mg before bed.
  • Melatonin – 500mcg timed release taken at 8:15pm (2 hours before bed)
  • PEA (PeaCure or Vitalitus brand) – 1 in AM, 1 with lunch.
  • Vitamin C 250mg – once per day (camu-camu or sodium ascorbate is what I use most).
  • Algonot PureLut – 1 gelcap with lunch
  • DAO – 1 with dinner or lunch, whichever meal is higher in histamine.
  • Magnesium – 2 capsules in the late afternoon.
  • 1 Vitamin D (1000mg) in AM when I take my quercetin and ketotifen.

Studies and science behind natural mast cell stabilizers

  • Brain “fog,” inflammation and obesity: key aspects of neuropsychiatric disorders improved by luteolin. (Study – Brain “fog,” inflammation and obesity: key aspects of neuropsychiatric disorders improved by luteolin). The same study also notes that luteolin protects against histamine release from mast cells
  • Palmitoylethanolamide  (works on the endocannabanoid system)
    • “The ability of PEA to control MC degranulation, via a CB1 ⁄ CB2 independent mechanism, has paved the way for its therapeutic use in both animals and humans. The PEA-mediated stabilisation of MCs has proven to be useful in the treatment of atopic and irritative dermatitis. In conclusion, we can hypothesise that cannabinomimetic compounds, including PEA and its congeners, act to control MC activation and degranulation early during the inflammatory response, thus leading to a swift resolution and preventing the development of chronic inflammatory disease.” (Study)
    • Palmitoylethanolamide is a potent mast cell stabilizer and pain reliever (Glia and mast cells as targets for palmitoylethanolamide, an anti-inflammatory and neuroprotective lipid mediator – study)
    • For those with other issues a potent neuroinflammation reducer too, acting synergistically within the endocannabenoid system. Overview /meta analysis, and neuroinflammation study: N-Palmitoylethanolamine and Neuroinflammation: a Novel Therapeutic Strategy of Resolution.
    • And luteolin PLUS Palmitoylethanolamide = even more stabilization. Study: PEA and luteolin synergistically reduce mast cell-mediated toxicity and elicit neuroprotection in cell-based models of brain ischemia. (This is the Mirica product above).
  • Binders, including zeolite, mentioned as a help for mopping up histamine here, and a specific post about how zeolite binds histamines here. See also Study – Histamine-binding capacities of different natural zeolites: a comparative study.
  • Rosae multiflora fructus extract stops mast cell release of histamine (rat study – Rosae Multiflorae Fructus Hot Water Extract Inhibits a Murine Allergic Asthma Via the Suppression of Th2 Cytokine Production and Histamine Release from Mast Cells – Study
  • Quercetin
    • Blocks histamine release due to chemotherapy drug. Study – Quercetin ameliorates paclitaxel-induced neuropathic pain by stabilizing mast cells, and subsequently blocking PKCε-dependent activation of TRPV1.
    • Quercetin also generally works for a wide range of allergies. Quercetin and Its Anti-Allergic Immune Response – study.
    • Quercetin works better than sodium cromlyn for stabilizing mast cells in certain conditions. Study: Quercetin Is More Effective than Cromolyn in Blocking Human Mast Cell Cytokine Release and Inhibits Contact Dermatitis and Photosensitivity in Humans.
    • Quercetin phytosome increases availability and allows for more meditator stabilization and cytokine blocking. Study: “Significant improvements in both in vitro solubility and oral absorption (in terms of both exposure and maximum concentration achieved) by healthy volunteers in a human clinical study were obtained with the Quercetin Phytosome formulation as compared to unformulated quercetin.”
  • Cannabinoid receptor agonists suppress mast cell release of histamine Study – Selective Cannabinoid Receptor-1 Agonists Regulate Mast Cell Activation in an Oxazolone-Induced Atopic Dermatitis Model. Also in the study “Cannabinomimetic Control of Mast Cell Mediator Release: New Perspective in Chronic Inflammation,”
  • Curcumin also acts as an antihistamine, and has been found to decrease mediator release by mast cells, when activated:
    • Anti-inflammatory effect of curcumin on mast cell-mediated allergic responses in ovalbumin-induced allergic rhinitis mouse (study)
    • Lipopolysaccharide (LPS) exposure differently affects allergic asthma exacerbations and its amelioration by intranasal curcumin in mice. (study)
    • Curcumin Ingestion Inhibits Mastocytosis and Suppresses Intestinal Anaphylaxis in a Murine Model of Food Allergy. (study)
    • Inhibitory eff ects of curcumin on passive cutaneous anaphylactoid response and compound 48/80-induced mast cell activation (study)
  • Vitamin C: Helps stabilize mast cells
    • Alison Vickery’s post about how Vitamin C can help increase DAO in the body, which then mops up histamine from food.
    • Article: The relationship between Vitamin C, Mast Cells and Inflammation:
      In the light of these studies, we found that vitamin C relieves most of the symptoms of diseases that involve activation of MCs and we can conclude that further research on the role of vitamin C and MCs is needed.”
    • Article: Vitamin C Revisited: “In critically ill patients, future research should focus on the use of short-term high-dose intravenous vitamin C as a resuscitation drug, to intervene as early as possible in the oxidant cascade in order to optimize macrocirculation and microcirculation and limit cellular injury.”
  • Nigella sativa (black cumin seed) blocks mast cell degranulation in rats (A study – “Effects of Nigella sativa seeds and certain species of fungi extracts on number and activation of dural mast cells in rats.”)
  • Probiotics that may help:
    • Lactobacillus G/G: study
    • Not a great site, but lists probiotics that trigger histamine release vs. those that are safe: here.
  • Vitamin E has been found to decrease mast cell degranulation in some studies. (study)

Safe Brands for Makeup, Cleaning Products, Laundry, and More

Because I’ve lived in both the USA and Canada with this condition, I’m listing out both products from Canada and the United States. This is what I’ve switched to, and this section came about from readers writing in for me to share what’s worked for me.


  • Study of Natural Mast Cell Stabilizers: a) chart (excerpt below) or, b) full study.
A chart of natural mast cell stabilizers like quercetin, luteolin, green tea extract, and more.


Generally:  an H1/H2 “blockade”, taken every 12 hours. Plus mast cell stabilizers and occasionally pain medication.

  • H1 blockers (Suggested to leave Benadryl for emergencies) – eg. Zyrtec, Xyzal, Claritin, Allegra, hydroxyzine, doxepin, loratadine, fexofenadine.
  • H2 blockers Famotidine (Pepcid), Cimetidine (Tagamet), Raniditine (MAR-Ranitidine)
  • Leukotriene inhibitors: Montelukast/Singulair
  • Prescription mast cell stabilizers (NOTE: per mast cell expert Doctor Theoharides, these are not full mast cell stabilizers as they do not block cytokine release, but have some mast cell stabilizing properties and mast cell doctors prescribe them as stabilizers often.)
    • Cromolyn sodium
    • Ketotifen (oral, compounded and by prescription in the United States and Canada). Teva makes a ketotifen oral tablet called Zatiden in Canada and other countries, which is prescription in Canada but OTC in many countries such as Mexico, Myanmar, India, and more. Zatidor eye drops are ketotifen as well, but in fumarate form and help symptoms in the eyes but will not help systemically. Average dosing from patients I’ve spoken to for oral tablets is 4-6mg per day in split dosing.

See the study Pharmacological treatment options for mast cell activation disease, as well as the suggestions in the Hoffman article from the overview section, here.

Further, the Mastocytosis Society has a list of pharmaceutical treatments that are common in mast cell disorders here.

Many mast cell patients react to excipients in traditionally-prepared pharmaceuticals, and therefore need to get their primary medication compounded. In addition, for patients in the USA where ketotifen is not available generally, a compounding pharmacy is needed to access that medication. You can read more about compounding pharmacies here.


symptoms of mast cell activation disorders

(Source: “A Practical Guide for Treatment of Pain in Patients with Systemic Mast Cell Activation Disease”)

Throughout the entire pain communication network, mast cells are the gatekeepers of pain. Mast cells can communicate with neurons, glia cells, microglia, and vascular endothelial cells through mediators. They influence brain functions directly through histamine. Pain alone can thus increase mast cell degranulation. Mast cells and the nervous system influence each other’s responses through mediators and cytokines. In the periphery mediators can stimulate receptors, resulting in pain. This stimulates mast cell activation creating a feedback loop, resulting in neurogenic inflammation. Mast cells can recruit other immune cells, which release more mediators, boosting inflammation.

Extreme mast cell activation causes inappropriate mediator release and reactivity, causing an enormous range of reactions in all tissues and systems. Classical analgesics, most narcotics and nonsteroidal anti-inflammatory drugs (NSAIDS), can trigger MCAD and thus can be ineffective. (See chart 1 “TABLE 4” below)

Pain in Mast Cell Activation Disorders and how to treat them effectively without worsening mast cell degranulation
Source: study.

Pain perception in mast cell dysfunction should be treated by addressing the mast cell mediator-related causes. But pain is also one of the biggest mast cell triggers – so lowering pain levels is important.

Mast cell stabilizers, avoiding inflammatory foods, meditation: these have all helped me, and may help others before stronger drug therapy if that’s what you prefer, especially since neuropathic pain is so hard to treat. (Personally, I went from 24/7 burning pain all over my body to none, unless I consume/am around something that angers mast cells.)

The relationship of mast cells and pain
Mast cells and pain. Source: EMBRN

Neuropathic pain poorly (if at all) responsive to classical drug management in the case of mast cell activation, as shown in the table below. Moreover, some of those drugs may worsen the severity of symptoms by further increasing mast cell activity.

Some of the drugs used to treat mast cell conditions (and some that make the symptoms worse)
Source: study.

Mast cells and Pain in Fibromyalgia

A 2019 study concludes that mast cells are key players of neuroendocrine and painful disorders, including fibromyalgia, and that inhibiting mast cells would be a useful tool in treating fibromyalgia.

 Natural molecules could include the flavonoids, luteolin and tetramethoxyluteolin, alone or in combination with other substances selected to reduce stress Other natural molecules could include palmitoylethanolamide, which apparently inhibits neuro-inflammation and reduces pain.” Source: “Mast Cells, Neuroinflammation and Pain in Fibromyalgia Syndrome

Mast Cells and Pain in IBS

A 2021 study in Nature entitled “Local immune response to food antigens drives meal-induced abdominal pain” concludes that researchers have identified the biological mechanism that they think may explain why some people experience abdominal pain when they eat certain foods. The studies, from KU Leuven, were carried out in mice and in humans and point to local mast cell activation. This local immune response includes the release of histamine and other mediators (as set forth in this resource page) which lead to pain and discomfort. The researches feel that the findings could pave the way to the development of more efficient treatments for IBS and other food intolerances, and are currently pursuing a larger clinical trial of antihistamine treatments.

An open access piece that accompanies the study, called “Food for thought about the immune drivers of gut pain”, notes that while debilitating gut pain is common, the underlying cause is often unclear. This new mast cell study points to a localized immune response that cause normally innocuous foods to be perceived as harmful, leading to persistent pain.

mast cells, histamine, and IBS in those who have had infection or harmful gut bacteria
An immune response to harmless food causes pain. The 2021 study reveals “a previously unknown cause of gut pain. a, Immune cells in the gut, including mast cells, which contain histamine molecules, don’t usually target food or microorganisms that normally reside there (commensal bacteria). If mice are infected with the bacterium Citrobacter rodentium, immune cells respond when the gut barrier breaks down (gut cells lose their connectivity), and food and bacteria leave the gut lumen and enter the body. Immune cells target C. rodentium by releasing defence molecules, and also target the harmless food present by producing antibodies that recognize it. Pain occurs as a result of the infection. b, After infection, repair of the gut barrier begins. Mast cells become primed to respond by moving near to neurons and expressing a receptor (generated on the basis of the antibody made previously) that recognizes a fragment of the food called an antigen. c, On subsequent ingestion of the food, mast cells recognize it and release histamine through a process called degranulation. Histamine binds to a receptor on sensory neurons, activating them and causing pain.” Source: Nature.

The article notes that:

People with IBS had more mast cells in close proximity to nerve fibres compared with healthy individuals, suggesting more-effective transfer of information between the mast cells and nerve endings of the sensory neurons.

And suggests that as a result of the data provided by this study, treatments for IBS may in the future include:

  • improving the gut permeability to reduce gut access to the intestinal immune system (what healing ‘leaky gut’ focuses on);
  • targeting IgE antibodies that are specific to the food substance of interest;
  • reducing mast-cell degranulation (the topic of this page!);
  • targeting the specific molecules released by mast cells; and
  • blocking the colonic sensory nerves that transmit information and cause pain.


This section explains how mast cell degranulation can lead to inflammatory responses that result in anxiety and/or depression or other neuropsychiatric responses. It is also why low inflammation and low histamine diets can be useful, and ties in to the “symptoms of MCAS by body area” section, above.

  • Dr Theoharides believes CRH stimulates the mast cells in the hypothalamus (and elsewhere) to produce something called vascular endothelial growth factor (VEGF), which then increases the permeability of the blood-brain barrier (BBB). That leaky BBB then allows more immune cell (e.g. mast cell) and perhaps pathogen infiltration into the brain and bingo, you have inflammation. Source: Could the Brain’s Mast Cells Be Causing Chronic Fatigue Syndrome (ME/CFS)?.
  • Mast cells are both sensors and effectors communicating between the nervous, vascular, and immune systems. In the brain, they live in the “brain side” of the blood-brain-barrier, and there they interact with astrocytes, microglia, and blood vessels via their mediators and chemicals. They are first responders in the body, catalyzing reactions, amplifying responses in the body, and also recruiting OTHER immune responses once they’re activated. When dysregulated, this contributes to neuroinflammation. See also the next study.

    “Mast cells both promote deleterious outcomes in brain function and contribute to normative behavioral functioning, particularly cognition and emotion. Mast cells may play a key role in treating systemic inflammation or blockade of signaling pathways from the periphery to the brain.”
    Source: Mast Cells and Neuroinflammation“.

  • Mast cells are implicated in brain injuries, neuropsychiatric disorders, stress, neuroinflammation, and neurodegeneration. Source: Mast Cell Activation in Brain Injury, Stress, and Post-traumatic Stress Disorder and Alzheimer’s Disease Pathogenesis.
  • An enhanced interaction between mast cells and nerves can lead to neurogenic inflammation. Inflammatory models have shown a significant increase in the number of mast cells, resulting in the increased release of inflammatory mediators on degranulation.

    “Inflammatory mast cell mediators may modulate sensory nerves through the activation of receptors on nerve terminals. […] Thus, mast cell activation can result in an increase in the excitability of sensory nerves and the production and secretion of neuropeptides.”
    Source: Significance of Conversation between Mast Cells and Nerves

  • Mast cells play a crucial role in the peripheral inflammation as well as in neuroinflammation due to brain injuries, stress, depression, and PTSD. Therefore, mast cells activation in brain injury, stress, and PTSD may accelerate the pathogenesis of neuroinflammatory and neurodegenerative diseases including Alzheimer’s disease. Mast cells in brain injuries, stress, and PTSD may promote the pathogenesis of Alzheimer’s disease. “We suggest that inhibition of mast cells activation and brain cells associated inflammatory pathways in the brain injuries, stress, and PTSD can be explored as a new therapeutic target to delay or prevent the pathogenesis and severity of Alzheimer’s disease.” Source: Mast Cell Activation in Brain Injury, Stress, and Post-traumatic Stress Disorder and Alzheimer’s Disease Pathogenesis
  • From 2021, inflammation dampens levels of a ‘feel-good molecule’ (serotonin) and antidepressants’ ability to boost them, according to new research in mice. The findings, from researchers at Imperial College London and University of South Carolina, add to mounting evidence that inflammation, and the accompanying release of the molecule histamine, affects a key molecule responsible for mood in the brain — serotonin. The study’s lead author noted, “Inflammation could play a huge role in depression, and there is already strong evidence that patients with both depression and severe inflammation are the ones most likely not to respond to antidepressants. Study: Inflammation-Induced Histamine Impairs the Capacity of Escitalopram to Increase Hippocampal Extracellular Serotonin.
  • And from another publication called Mast cell disorders: From infancy to maturity: “Mast cells are also establishing a newfound importance in severe asthma, and in remodeling of blood vessels in cancer and atherosclerotic vascular disease. Furthermore, recent evidence suggests that mast cells sense changes in oxygen tension, particularly in neonates, and that subsequent degranulation may contribute to common lung, eye, and brain diseases of prematurity classically associated with hypoxic insults.” This article is a review of mast cell disorders and chronic inflammatory conditions that involve mast cell dysfunction.
  • As cited in the “anxiety” section, an October 2023 study, Neuropsychiatric Manifestations of Mast Cell Activation Syndrome and Response to Mast-Cell-Directed Treatment: A Case Series saw patients experience significant improvements regarding neuropsychiatric symptoms, including anxiety and depression, after mast-cell-directed therapy.


  • Mast cells associated with onset of celiac [study]. “We provide a description of the progressive stages of Celiac Disease, in which mast cells are the hallmark of the inflammatory process. Thus the view of Celiac Disease, should be revised, and the contribution of mast cells in the onset and progression of Celiac Disease, should be reconsidered in developing new therapeutic approaches.”
  • A review of studies that each investigate the role of mast cells in the pathogenesis of coeliac disease, showing that these cells increase in number during the progression of the disease and contribute to define a pro-inflammatory microenvironment. A similar conclusion to the one above. [study] “In conclusion, it can be assumed that mast cells represent one of the main players of the intestinal damage in the onset of Celiac Disease. Hence, the pathogenesis of Celiac Disease should be revised and the contribution of mast cells in the onset and progression of the disease should be considered in the planning of new therapeutic approaches.”
  • A 2020 study called Coeliac Disease Pathogenesis: The Uncertainties of a Well-Known Immune Mediated Disorder looks at the different ways that the disease can develop, and what parts of the immune system and body are involved. The study looks at cytokines (IL-15), gamma/delta T-cells, mast cells, and more.”There is also evidence that cells of the innate immune system, including eosinophils, mast cells and neutrophils, contribute to disease pathogenesis.” [study]
  • Intestinal mast cell involvement with celiac disease [study].
  • Mast cells also involved in dermatitis herpetiformis, a chronic, itchy, blistering skin condition that is a skin manifestation of celiac disease. Patients with dermatitis herpetiformis usually lack the gastrointestinal symptoms of traditional celiac disease, but it is nonetheless linked. Mast cells gone rogue will active inflammation excessively, causing tissue damage. Studies have found that this pattern directly contributes to conditions like dermatitis herpetiformis.


Part of what led me to write this page was the prevalence of mast cell issues within the leaker community. That community is primarily made up of “long haul” leakers like me, people with connective tissue dysfunction or some other genetic and/or pathogenetic reason that the body isn’t able to seal and heal the dura robustly, even with intervention.

It turns out that continuous mast cell degranulation can affect the connective tissue adversely, and for patients with connective tissue disorders that’s a double whammy.

What is Ehlers Danlos Syndrome?

It’s often written in the singular, but it’s actually plural, as there are currently 13 different classifications of Ehlers-Danlos syndromes (EDS), most of them heritable (inherited) conditions. The most common types are hypermobile EDS (hEDS) and classical EDS. For now, genes for hEDS have not been identified, so this type of EDS is diagnosed by ruling out other types plus with a criteria for clinical analysis that was updated in 2017 and includes specific characteristics of hEDS.

The genes for the other types, as well as inheritance pattern, are identified below:

genes associated with with Ehlers-Danlos syndromes
© 2023 The Ehlers Danlos Society. Source.

Since EDS is a connective tissue disorder that causes defects in collagen / abnormal collagen synthesis, and as collagen is found throughout the body and tissues, having EDS can affect your whole body, including bones, endothelial system, organs, joints, and skin. While some practitioners erroneously think that EDS “just means you’re flexible”, in actuality it affects many body systems in important ways. Like MCAS, the EDS types only have management of symptoms on offer—not a cure.

With each of the types of EDS, there are different symptoms (although there is still some overlap), as set out in the chart above. Joint hypermobility, skin stretchiness (called hyperextensibility), poor wound healing, and tissue fragility are common among multiple types of EDS. There are “stiff” EDS patients, especially if the patients are older. In vEDS (the vascular EDS type), the cardiovascular system is especially affected. Classical EDS has many skin changes and symptoms.

MCAS and Connective Tissue

When mast cell degranulation happens it not only releases histamine but also proteases, which are enzymes that lead to the breakdown of proteins into smaller polypeptides or single amino acids. Since mast cells live all over the body in tissues, this can affect the integrity of that tissue over time.

We know that EDS affects connective tissue, in some cases quite aggressively. Mast cells live in connective tissue throughout the body, so it follows that having disordered connective tissue would also affect mast cells in some way.

MCAS and EDS: A review of the literature.
From: Association of mast-cell-related conditions with hypermobile syndromes: a review of the literature: “Aberrant mast cell (MC) activation can produce inflammatory changes at the connective tissue level leading to dysfunction in multiple organ systems. In peripheral nerves, MC can localize to epineurium, perineurium, and endoneurium and release mediators which may activate nociceptors producing symptoms such as peripheral neuropathy and headache (a). MC-mediated upregulation of cytokines can lead to dysfunctional fibroblast proliferation in nasal and bronchial tissue leading to rhinitis and sinusitis (b). MC-induced TGFB upregulation and localization within bronchial smooth muscle cells can cause modification of matrix proteins of bronchial parenchyma contributing to tissue damage and Asthma (c). MC-induced TGFB upregulation in esophageal tissue can cause proliferation and smooth muscle contraction contributing to eosinophilic esophagitis symptoms (d). When MCs are localized to connective tissues, they can cause microenvironmental changes to the extracellular matrix, inducing IgE medicated autoreactivity and contributing to rheumatologic conditions such as rheumatoid arthritis and systemic lupus erythematosus (e). MC-induced changes may contribute to laxity within blood vessels, causing pooling of the blood in extremities, contributing to postural tachycardia syndrome (POTS) in which patients experience increase of heart rate with standing, a finding commonly associated with hEDS (f)”
  • Several investigators have noted a possible link between EDS and MCAD, primarily patients with the hypermobility type of EDS. This study examines whether the fact that mast cells live in connective tissue, combined with the “wonky” connective tissue of EDSers means that mast cell activation is more common because of the changes in structure of connective tissue in primarily hEDS patients. Full 2017 study hereby Doctor Maitland and Doctor Afrin.
hEDS: signs, symptoms and comorbidities, via CortDoesScience
  • After being recruited to connective tissues, mast cells go through more change when they are influenced by surrounding cells. And many mast cells live in our connective tissues. This 2017 study looks into how dysregulation of the mast cells occurs in connective tissue disorders.


As noted in the long Covid section, below, Dr. Theoharides’ December 2023 paper postulates that mast cell treatment may benefit patients with conditions of the autonomic nervous system (ANS) such as postural orthostatic tachycardia syndrome (POTS). Back in 2005, a small study found that patients improved clinically when treated with H1 and H2 histamine receptor blockers (with or without α-methyldopa), and concluded that:

“With regard to the pathophysiology underlying the association between POTS and MCA, we propose a positive feedback loop by which MCA, with the subsequent release of vasoactive mediators, may contribute to vasodilation, reflex sympathetic activation, central volume contraction, norepinephrine release, and orthostatic intolerance.”

mast cells and POTS: a correlation?
Proposed pathophysiological mechanisms underlying the association between MCA and hyperadrenergic orthostatic intolerance. Source.

These findings are interesting for many reasons, but in part because some patients that write me who have POTS say they’re often worse with beta blockers (β-blockers), commonly used in the treatment of POTS patients. This paper says beta blockers should be used with caution for patients with both conditions. Supplementing this is a note from the excellent MastAttack, where author Lisa Klimas notes the use of beta blockers in patients with risk of anaphylaxis requires some special consideration, because they “directly block many of the places where epinephrine works to mitigate anaphylaxis.” This means that using epinephrine to treat the anaphylaxis may be ineffective.

While the ANS does appear to be influenced by mast cells, there aren’t many papers on the extend thereof, so I will update this section if new ones come out.


  • In a review article called Curbing Inflammation in Multiple Sclerosis and Endometriosis: Should Mast Cells Be Targeted?, the author discusses how many inflammatory diseases are fuelled by both internal and external stimuli, and begin as inflammation and then progress to a disease state following tissue damage and more. Many different cell types are involved depending on the disease, but mast cells are usually one of them (in both the acute inflammation and in the disease state). “Recent studies in porcine and rabbit models have supported the concept of a central role for mast cells in a “nerve-mast cell-myofibroblast axis”, article notes, playing a big role in the inflammatory process that leads to disease.

Elevated levels of mast cell products have been detected in fluids from MS patients. These include mast cell tryptase in CSF from MS patients and histamine levels in CSF from MS patients. In spite of such evidence, the role of mast cells in MS is still somewhat controversial.

The article concludes based on what it discusses that targeting mast cells in both MS and endometriosis “may be a fruitful avenue to control the recurring inflammatory exacerbations of the conditions.”

  • Another study from April 2019 called Mast Cells in Neurodegenerative Disease notes that neuroinflammation is well-established now as a primary pathological component of diseases such as multiple sclerosis, and is gaining acceptance as an underlying component of most, if not all, neurodegenerative diseases. Before, studies focused on the glial cells of the central nervous system, but now researches are looking at mast cells as well, since mast cells affect both their microenvironment and neighbouring cells including T cells, astrocytes, microglia, and neurons. And they can also disrupt and change the permeability of the blood brain barrier, which “has the potential for dramatically altering the neuroinflammatory state,” per the study.
  • Role of Mast Cells in the Pathogenesis of Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis, from 2017, discusses how mast cells may act at the early stages of ME or EAE to promote demyelination. The study concludes that depleting or limiting mast cells could be a new promising therapeutic target for MS and EAE.
  • Another study from 2020 reviews the relationship between mast cells and angiogenesis in multiple sclerosis.
  • From 2016, a study called Important role of mast cells in multiple sclerosis. “Autoimmunity is a disease that occurs when the body tissue is attacked by its own immune system. Multiple sclerosis (MS) is an autoimmune illness which triggers neurological progressive and persistent functions.” MS is associated with an abnormal B-cell response and upregulation of T-cell reactivity against a multitude of antigens, and since mast cells are the 1st line of defense in the innate immune system, their participation in the central nervous system is now the subject of much research. Per the study, “[t]hey have an important role in autoimmune disease, including MS where they mediate inflammation and demyelinization by presenting myelin antigens to T cells or disrupting the blood-brain barrier and permitting entry of inflammatory cells and cytokines. The participation of mast cells in MS is demonstrated by gene overexpression of chemical mediators and inflammatory cytokines.


One of the worst symptoms for me when my mast cells were uncontrolled was painful tingling, burning, or even lack of feeling in my feet and sometimes hands, usually at night. While I didn’t know it at the time, small fiber neuropathy (SFN) can cause this kind of nerve pain or nerve activation. It was very hard to fall asleep with the level of pain caused.

I have seen many mast cell patients get tested for SFN over the years, and their biopsies were almost always positive. Happily, these symptoms resolved for me with my MCAS protocol, but I was very interested in a March 2022 study that looked at SFN in people with mast cell activation syndrome or hereditary alpha tryptasemia. From the study:

Reduced nerve fibers consistent with SFN were found in 80% of patients with HαT and 81% of those with MCAS. Mild-to-moderate dysautonomia was detected in all patients with HαT and MCAS when results of sympathetic, parasympathetic, and sudomotor tests were combined.

Mast cell disorders are associated with decreased cerebral blood flow and small fiber neuropathy. March 2022.

I created this subheading for SFN because its existence in mast cell patients is so high that it is likely to be a symptom many readers here experience.


I get emails about eczema often, from people who say they know it’s “not a mast cell issue” but they’ve got a lot of skin symptoms and they wondered if I could point them. inthe right direction.

Eczema (atopic dermatitis – “AD”) is too is thought to be partly mast cell mediated. The condition is a chronic or chronically relapsing pruritic (itchy) inflammatory skin disease. While clinical manifestations vary with age, in early childhood often it begins with eczematous lesions on the cheeks and the scalp. Later in the childhood, lesions can develop especially at the nape of the neck, and the elbows and knees. In adolescence and adulthood, “lichenification” (a thickening of the skin with more red and flaky skin markings) often develops.

Throughout, the lesions cause a consistent itch that leads to sleep deprivation and skin changes, and can substantially affect people’s quality of life. The National Eczema Association estimates that 1 in 10 individuals will develop eczema during their lifetime.

So where do mast cells come in? An earlier (2012) study found that that mast cells are important in initiating and maintaining skin inflammation of AD induced by IL-1, likely through induction of TSLP and IL-4. In a 2019 study, researchers found that intestinal biopsies from four children with atopic dermatitis contained more mast cells than those from four children without the condition, linking mast cells and food allergies with AD. Another 2019 study found that AD patient’s skin biopsies had significantly increased mast cells compared to non-diseased control skin tissues, and that those mast cells were activated.

The figure below also shows how mast cells act as potential sources of inflammatory and/or regulatory mediators during development of various cutaneous infections and diseases, via a review of the role of mast cells in skin diseases:

mast cells and cutaneous diseases: roles and sources of inflammation
Source: Roles of Mast Cells in Cutaneous Diseases, Fig 7, Front. Immunol., 06 July 2022 Sec. Inflammation Volume 13 – 2022

There is a 2023 push to see what blocking Mas-Related G-Protein Coupled Receptor X2 (MRGPRX2) does — it is a receptor on mast cells themselves. The theory is that by blocking activation of MRGPRX2, EP262 has the potentially block mast cell degranulation and treat a broad range of mast cell mediated diseases. The studies are focusing on chronic urticarias (hives) and atopic dermatitis (eczema) first.

Also, scientists in 2023 discovered a “new sense of touch”. Researchers from Imperial College London in the UK, used an RNA sequencing process to find that cells in part of the hair follicle called the outer root sheath had a higher percentage of touch-sensitive receptors than equivalent cells in the skin, and that those root sheaths released serotonin and histamine through adjacent vesicles, as a way of signaling to the surrounding cells. Since we know that histamine plays a significant role in several inflammatory skin diseases (like eczema), perhaps research into these hair follicles can help us understand more about how to treat them.


As mentioned above, Covid and other viruses can lead to post-viral mast cell activation and mast cell dysfunction. Some mast cell experts believe that a chunk of long-Covid symptoms are due to dysfunctional mast cells. In addition, there is more and more research about microclotting and vascular issues after covid, something seen in a wide variety of MCAS patients.

For starters, see a long thread linking out to general resources about long covid. It doesn’t mention mast cells specifically, though. So, where to mast cells come in? In a September 2020 study from doctors Afrin, Weinstock, and Molderings, the conclusion notes:

The prevalence of MCAS is similar to that of severe cases within the Covid-19-infected population. Much of Covid-19’s hyperinflammation is concordant with manners of inflammation which MC activation can drive. Drugs with activity against MCs or their mediators have preliminarily been observed to be helpful in Covid-19 patients. None of the authors’ treated MCAS patients with Covid-19 suffered severe infection, let alone mortality.

In addition, please see:

  • Potential association of mast cells with coronavirus disease (2019).
  • Covid-19 hyperinflammation and post-Covid-19 illness may be rooted in mast cell activation syndrome (2020, discussing how both severe outcomes and PAS-C / long haulers may have unruly mast cells as the root of their hyperinflammation).
  • Mast cell activation symptoms are prevalent in Long-COVID (2021). Study concludes that MCAS symptoms were increased in long covid, and that they mimicked the symptoms and severity reported by patients who have MCAS. “Increased activation of aberrant mast cells induced by SARS-CoV-2 infection by various mechanisms may underlie part of the pathophysiology of LC, possibly suggesting routes to effective therapy.”
  • I’ve heard from MANY readers who say they have increased insomnia and anxiety post-Covid, and finding it hard to get to baseline. Their practitioners are simply telling them that they are stressed. As discussed in this page, excess histamine and other mast cell mediators can lead to many symptoms, including insomnia and anxiety. Readers discuss it as a “chemical anxiety”, not one that’s in response to a specific stimuli but rather something that just “is” for reasons they can’t understand. The increase in inflammation and mast cell activity post-Covid for some patients may be behind these new symptoms. Quite a few have landed on mast cell activation treatment as a way to mitigate these new symptoms, and have found their anxiety levels returned to baseline.
  • Histamine is part of what helps SARS-COV-2 enter the cells, says a 2022 study that also recommends an H2 blocker, famotidine, to help mitigate against severe outcomes. “H]istamine and histamine receptor signaling is likely essential for spike protein to induce ACE2 internalization in endothelial cells and cause endothelial dysfunction and that this effect can be blocked by the H2R blocker, famotidine.

And, a case report called Mast Cells and COVID-19: a case report implicating a role of mast cell activation in the prevention and treatment of Covid-19 follows a patient who had a history of dysfunctional mast cell activation symptoms but never had laboratory confirmation of the condition— until she contracted COVID-19:

This case illustrates the need to recognize the rate of mast cell activation in SARS-CoV-2 infection, not only to optimize anti-SARS-CoV-2 therapy, including the development of vaccine, but to potentially curb the risk of SARS­ CoV-2 triggered hyperinflammatory syndrome.

As to the microclotting and “sticky blood” some of you have written in about: a case study from 2021 called Persistent Antiphospholipid Antibodies, Mast Cell Activation Syndrome, Postural Orthostatic Tachycardia Syndrome and Post-COVID Syndrome: 1 Year On concludes that this may be an area of further research, something many ME/CFS researchers have been banging the drum about since COVID-19 began.

Cort Johnson, who runs an excellent blog about ME/CFS, wrote about this potential complication of COVID-19, and summarizes the research up until publication date (2021) about endothelial damage and sticky blood in both long covid and ME/CFS. He also has a long covid resources page, here.

In addition, a preprint from June 8, 2022 discusses similar findings to covid-19 —microclotting—in post-viral ME/CFS patients.

microclots in long covid and me/cfs
From The occurrence of hyperactivated platelets and fibrinaloid microclots in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), June 8, 2022.

In a 2023 paper entitled, Mast cells in the autonomic nervous system and potential role in disorders with dysautonomia and neuroinflammation, Dr. Theoharides and his team note that mast cells can be stimulated by the autonomic nervous system (ANS) and that the ANS can also affect the release of “neurosensitizing, proinflammatory, and vasoactive mediators” by mast cells. The paper posits that mast cells may be able to regulate certain functions that are dysfunctional in other conditions that affect the ANS, including postural orthostatic tachycardia syndrome (POTS) and long Covid. Therefore, the paper suggests that potential avenues of treatment for those conditions should include inhibiting mast cell activation.


I’ve shared studies linking mast cells to IBS and fibromyalgia pain, as well as to a few specific conditions. In addition, mast cells have been implicated in a variety of other conditions. In a 2022 paper by mast cell specialist Dr. Molderings, he notes:

Of note, MCAD is often accompanied by more or less frequent comorbidities such as dysferlinopathy, sarcoidosis, Ehlers-Danlos syndrome, sickle cell disease, Segawa syndrome , chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME), fibromyalgia syndrome (FMS), autism, or neurofibromatosis, all of which have in common genetic distortions as causes of the disease.

This paragraph refers to the umbrella of mast cell diseases, including those with high tryptase as the norm. It does not mean having those conditions means you have a mast cell issue so much as it working on suppressing mast cells may effectively provide relief of some symptoms involved in the diseases that are related. I’ve linked to some studies or review articles for some of those conditions below.

When you think about the fact that mast cells are found throughout the body and brain, it makes sense that they would have a critical impact on a variety of conditions that relate to the nervous system, immune system, or tissues.

Among them:

  • Vulvodynia – see here (also covers interstitial cystitis) and here.*
  • Interstitial cystitis – see here and here.*
  • Autism – see here.
  • Postural Orthostatic Tachycardia Syndrome – see here, and the COVID-19 section, above.
  • Sarcoidosis – see here.
  • Osteoarthritis – see here.
  • Chronic hives / itching – see here.
  • Restless Leg Syndrome – see here.
  • Peripheral neuropathy – see here and here. (For bad flares, I often get painful tingling and burning in my hands and feet). This is also very common in EDS patients, in part due to the laxity in tissues causing a lot of pressure on the peripheral nerves, but now research has established that an association with mast cell disorders is also part of the equation.
  • Endometriosis – see the study from the MS section, above, and here.
  • Arthritis – see here.
  • Migraines – see here, with full study here.
  • Trigeminal neuralgia – see here.
  • Asthma specifically – see here.
  • I’m including tinnitus again here, because some patients consider it a symptom whereas others see it as a separate issue. It’s common in mast cell activation disorder—prevalence of tinnitus in one prospective study by mast cell experts was 61.4%, compared to 9.6% in the general population.
  • Rosacea – adaptive immunity, along with the innate immune system, might play a critical role in the pathophysiology of rosacea; past studies have shown that mast cells can heighten host defense by initiating inflammation associated with innate immune responses. Increasing evidence has indicated that mast cells have important effects on the pathogenesis of rosacea. See here.

*Per pelvic pain and vulvodynia foundations, patients with interstitial cystitis and/or vulvodynia may benefit from a low-oxalate diet. (See here) That diet is set out in the ‘treating mast cells naturally’ section above.


Does this page sound very familar to you, and you also have a terrible time with sleep? You’re not alone. Mast cell research has shown that the cells are controlled by their own “internal clock”, regulated by clock genes just like other organs in the body. This circadian clock regulates many things in the body, and since mast cells themselves have a circadian expression, it’s important to look at them when it comes to sleep as well.

Mast cells are controlled by their clock genes, but also by the factors I’ve set out in this article — things like diet, triggers, and also hormones. In addition, histamine also plays a role in the regulation of sleep phases. So mast cells are very involved in sleep and wakeful times.

My sleep was terrible for most of my life, until I got my mast cells under control. I would have racing thoughts before bed, keeping me awake well into the night. As my mast cell issues got worse during the onset of the CSF leak, attempts to fall asleep were futile until 4-5am in the morning. Prior to that, I would feel wide awake or if I started to doze off, I would gasp awake again physically jerking my body away from sleep. Of course, this was not done intentionally and I thought it was simply anxiety.

But it turns out the anxiety that I thought I had? It was vastly physiological. When I put the protocol I share above into place, I was able to sleep again. I was no longer dealing with the myoclonic jerks before sleep. I was no longer dealing with racing thoughts before bed. I was no longer waking up at 4am if I did manage to fall asleep.

It turns out it was mast cell issues all along. This makes sense, because histamine not only affects sleep/wake cycles but peaks around 3am. It also promotes wakefulness, so if it’s extra high in someone with a mast cell disorder where it’s insufficiently synthesized in the body or in levels of excess, it makes sense that insomnia (and a racing heartbeat, changes in temperature, blood pressure, and flushing) would follow.

For more see my long article about jet lag, mast cells, and immune cellswhich includes a thorough jet lag protocol to minimize the circadian rhythm disruption both for day-t0-day life, and when traveling.

COVID-19 and Chronotherapy

Increasingly, scientists are looking to the circadian rhythm of the body to help manage the diseases of the present, and the treatments of the future.

“When we saw the controversy surrounding the use of ibuprofen, we wanted to fully understand why this drug was beneficial to some people, but having negative effects on others,” said Harry Karmouty-Quintana of University of Texas Health. In a report published in the British Journal of Pharmacology called The case for chronotherapy in Covid-19-induced acute respiratory distress syndrome, Harry’s team suggests providing anti-inflammatory medicine at specific times of the day, which would impact the body’s response to the medication without interfering with its fight against COVID-19.

“We hypothesize that the intrinsic circadian clock of the lung and the immune system may regulate individual components of CRS, and thus, chronotherapy may be used to effectively manage ARDS in COVID-19 patients,” notes the study – which dovetails well with the sections on mast cells, below. We know mast cells have their own circadian rhythm, and that they release cytokines when they degranulate (release inflammatory substances into the blood). It follows, per Harry’s team, that administering medication based on the schedule of that inflammatory flood could optimize the body’s attempts to heal.

Per the conclusion:

“This would mean that afternoon is the preferred time window for drug administration whereas intake at night should be avoided. This is particularly important when administering immune modulators where a single dose is usually given. Furthermore, the goal of chronotherapy in COVID-19 is to avoid reaching steady-state drug levels; as in the case of anti-inflammatory therapy, these would dampen the inflammatory response directed towards the virus.”

Based on what doctors know about the circadian clock of immune cells, they think that time timing of anti-inflammatory agents are important. This is because the immune cells release cell signals associated with negative effects to the body during the mid-to-late afternoon, but release antiviral molecules during the night and into the early morning. A “therapeutic window” for medication would give the medication an opportunity tamp down on inflammation that harms, while also allowing immune cells to produce the inflammatory molecules needed to fight the virus at night.


  • Breathing: pranayama breathing (PDF) or Butyeko breathing method (introduction here):
    • Treatment of mast cells with carbon dioxide suppresses degranulation via a novel mechanism involving repression of increased intracellular calcium levels. [Study breathing increases Co2]
    • Evidence-Based Role of Hypercapnia and Exhalation Phase in Vagus Nerve Stimulation: Insights into Hypercapnic Yoga Breathing Exercises [Study article – “Research has shown that vagal stimulation helps you not only in controlling the health of your organs and tissues, but it also determines the growth of your stem cells which, in turn, help body in repairing and replacing damaged cells”]
  • Meditation: see my 10-week free course with guided tracks for beginners, if you’re just getting started.
    • A comparison of mindfulness-based stress reduction and an active control in modulation of neurogenic inflammation [study]
    • Meditation and vacation effects have an impact on disease-associated molecular phenotypes [study]
  • Dynamic Neural Retraining System. Some mast cell practitioners recommend DNRS as a means of reducing overall stress and reactivity to triggers, not to ‘cure’ MCAS (as it has no cure) but to help lower the overall level of burden on the body. This is a practice related to neuroplasticity, but is not without controversy.
  • EMDR / trauma therapy or somatic experiencing therapy
  • Intermittent fasting. Not recommended to try multi-day water fasts, as histamine levels start rising again with too much fasting. However, restricting eating to an 8-hour or 6-hour window does seem to benefit.


The two most helpful books I’ve read about mast cells are:


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