When Mycotoxins Are Triggering Your MCAS

This post discusses why mycotoxins are triggering your MCAS, and what to do if they are.

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What is MCAS?

Mast Cell Activation Syndrome (MCAS) is a chronic condition that affects all organ systems. It can cause severe, disabling symptoms every day, including potentially fatal anaphylaxis. MCAS often occurs with other chronic conditions like Ehlers-Danlos Syndrome (EDS) and Postural Orthostatic Tachycardia Syndrome (POTS). Managing MCAS is challenging because many healthcare providers are unaware of it, and diagnostic tests can be unreliable. Treatments involve using antihistamines, mast cell stabilizers, and avoiding triggers. Check out this post on how to manage MCAS.

Why mycotoxins?

As I discuss in this post, mold toxicity is suspected to be the number one trigger for MCAS.

Mycotoxins are toxic substances produced by certain molds and fungi. They can contaminate food and living spaces, and cause serious health problems in humans and animals. 

How mycotoxins occur

• Mycotoxins can grow on crops like cereals, nuts, spices, dried fruits, and coffee beans.
• They can also grow in animal food, such as corn.
• Mycotoxins are more likely to grow in warm and humid conditions.

Health effects of mycotoxins

• Mycotoxins can cause acute poisoning, immune deficiency, and cancer.
• Symptoms include headaches, abdominal pain, vomiting, diarrhea, chronic fatigue, and brain fog.

Mycotoxins and MCAS

Mycotoxins, toxic compounds produced by mold, can trigger or worsen mast cell activation syndrome (MCAS) through several mechanisms. Here’s how:

Direct Mast Cell Activation

• Mycotoxins stimulate mast cells, leading to the release of histamine, tryptase, prostaglandins, and other inflammatory mediators.
• Some mycotoxins, like ochratoxin A, aflatoxins, and trichothecenes, have been shown to directly trigger mast cell degranulation.

Increased Histamine Load

• Many mycotoxins impair the body’s ability to break down histamine (by inhibiting DAO and HNMT, the main histamine-degrading enzymes).
• This leads to higher histamine levels, which worsens MCAS symptoms like flushing, itching, and digestive issues.

Immune System Dysregulation

• Mycotoxins suppress regulatory immune pathways, leading to an overactive and hypersensitive immune response.
• Chronic mold exposure can shift the immune system toward a Th2-dominant state, which promotes allergic reactions and mast cell overactivity.

Increased Gut Permeability (“Leaky Gut”)

• Mycotoxins can damage the gut lining, leading to leaky gut syndrome.
• This allows undigested food particles and toxins to enter the bloodstream, triggering mast cell activation in the gut and systemically.

Nervous System & Brain Inflammation

• Mycotoxins affect the nervous system, leading to neuroinflammation and mast cell activation in the brain.
• This contributes to brain fog, anxiety, dizziness, and chronic fatigue, all common in MCAS and mold toxicity.

Impaired Detox Pathways

• Many people with MCAS have genetic or functional impairments in detox pathways (e.g., MTHFR mutations, glutathione deficiency, or poor bile flow).
• Mycotoxins place a heavy burden on liver detox pathways, worsening mast cell instability and toxin buildup.

My mycotoxin situation

After several water incursions in our old home, my daughters and I became very sick. I had known all along that mold toxicity had triggered my MCAS. Last year I focused on healing my nervous system with the Safe and Sound Protocol, and my health improved significantly. But as I discuss in my book Rocks and Roots: Solo Backpacking My Way to Health on the Superior Hiking Trail (2024), I still reacted to sulfur-containing foods with inflammation, pain, and gut issues. Sulfur cycle dysregulation often happens when your detox pathways are overwhelmed with trying to detoxify mold from your body, and I suspected that was the case with me.

I decided that 2025 would be the year I got to the bottom of my mold issues. So I ordered a mycotoxin test through Mosaic Diagnostics, a simple urine sample test, that you mail in to the lab. Within ten days I had the results back showing that my levels for two mycotoxins were off the charts: Chaetoglobosin A (CHA) and Citrinin (Dihydrocitrinone DHC).

What is Chaetoglobosin A (CHA)?

Chaetoglobosin A is a mycotoxin produced by the fungus Chaetomium globosum. It is a highly toxic compound that can cause a range of health problems, including respiratory irritation, nausea and vomiting, diarrhea, liver damage, kidney damage, and cancer. 

Chaetomium globosum is the third most common indoor fungal contaminant of damp buildings. It has been isolated from several places such as soil, dung, feeds, foods, textiles, plywood, carpet, wallpaper, and wet walls.

Inhalation of airborne spores and CHA from this fungus is known to produce respiratory as well as systemic infection in human beings. Case reports of infections include mild to severe illness, from sinusitis, onychomycosis, and cutaneous infections to disseminated cerebral disease, pneumonia, and keratitis. Relatively low levels of CHA are lethal to various tissue culture cell lines and it is thought that CHA is highly toxigenic, even at minimal doses.

The health effects of CHA depend on the amount and duration of exposure. Acute health effects of CHA exposure include: 

• Respiratory irritation, including coughing, wheezing, and shortness of breath
• Nausea and vomiting
• Diarrhea
• Liver damage

Chronic health effects of CHA include kidney damage, cancer, and male infertility. 

To prevent exposure to CHA:

• Avoid water-damaged buildings.
• Keep soil and food dry.
• Use a dehumidifier to reduce moisture levels in damp areas.
• Remove mold promptly if it is found.

What is Citrinen?

Citrinin is a mycotoxin found in food and supplements. It can be harmful to the kidneys, liver, heart, and nervous system. 

Sources of citrinen include:

• Produced by the fungi Aspergillus, Penicillium, and Monascus
• Most commonly found in red yeast rice, a food additive made from fermented rice
• Can also be found in beans, fruits, fruit juices, herbs, spices, and dairy products

Health effects of citrinen

• Can cause nephrotoxicity and genotoxicity in humans and animals
• Can cause mitochondrial dysfunction, which can lead to organ system issues, such as those in the heart, digestion, and reproduction
• Can impede fertility and prevent pregnancy
• Can disrupt microtubule assembly in cardiac cells

Exposure 

• Ingestion of foods and supplements contaminated with citrinin can lead to prolonged exposure and health consequences

The bucket theory

The bucket theory simplifies understanding symptom reactions with MCAS. Imagine your body as an empty bucket you don’t want to overflow. Reactions to various stimuli fill the histamine bucket at different rates, forming the total histamine level (how full your bucket is). More histamine means more symptoms. By managing triggers, reducing exposures, and taking medications and supplements, you can control your bucket’s level.

Know your typical symptom progression

Knowing your symptom progression in a symptom flare is the key to developing your rescue plan. This post discusses how to recognize your symptom progression so you can be prepared to address those symptoms.

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Why did I have CHA and Citrinen?

I was not surprised with the results of my mycotoxin test because the mold we found in our former home had been growing on the wet wallboard in the basement. CHA is very common in homes with wet wood and paper, which is what our former home had.

I suspect that my citrinen toxicity comes from contaminated rice. I can’t tolerate rice, and rice products cause some of my more significant MCAS symptom reactions.

How to detox mycotoxins

So, how do you get the mycotoxins out of your body? Taking binders targeted to the specific mold species in your body can help to eliminate mold. General mycotoxin binders that work well for Chaetoglobosin A (CHA) include:

Activated Charcoal – Highly effective at adsorbing a broad range of mycotoxins, including fungal toxins. Best taken away from food and medications.

Cholestyramine (CSM) – A prescription bile acid sequestrant that binds fat-soluble toxins, including many mycotoxins. Compounded, dye-free versions are best for MCAS-sensitive individuals.

Bentonite Clay – Binds many mycotoxins, though less research is available on its effectiveness against CHA specifically.

Zeolite (Clinoptilolite) – A natural volcanic mineral that binds various mycotoxins and heavy metals.

Modified Citrus Pectin (MCP) – Helps with toxin elimination through the gut, particularly for lipid-soluble toxins.

Chitosan – A fiber-based binder that may help with fungal toxin elimination.

In addition to taking a binder, it is also important to support your body with supplements like glutathione and NAC, which support liver detox pathways, milk thistle, which protects liver function and promotes bile flow, and hydration and electrolytes, which help flush toxins effectively.

But because of my sulfur cycle dysfunction (caused by mold toxicity in the first place!) I knew I couldn’t tolerate glutathione, NAC, or milk thistle. I would have to just go slowly with binders, probiotics, and electrolytes.

My plan for detoxing mycotoxins

Once I knew which species of mold I had, and I’d researched which binders to use to detoxify them, I decided to start with Cholestyramine (CSM). I’d taken CSM for a couple of months when we first moved to our new home, but it wasn’t long enough. I had also recently been scanning old documents (paper) that were likely still contaminated with CHA from our former home. So, I was likely dealing with past CHA contamination as well as recent exposure.

My functional provider prescribed a three-month course of CSM. Because I tend to react to everything, I started slowly with just one 1/2 tsp. dose of CSM and then I waited to see if I would react. Sure enough, that night I had a significant MCAS flare, likely from the dyes, fillers, and colors in the generic brand of CSM I had gotten from my pharmacy.

Citrinen also can be detoxed by taking probiotics that crowd it out of the digestive tract. I already consume a probiotic-rich homemade yogurt, so for now I would focus on binders for the CHA.

What if you react to cholestyramine (CSM)?

People with Mast Cell Activation Syndrome (MCAS) can sometimes react to cholestyramine (CSM), but individual responses vary. Here’s why:

1. Histamine & Mast Cell Triggers – CSM binds to bile acids, which play a role in fat digestion. Some people with MCAS already have bile acid dysregulation, and altering this can trigger symptoms. CSM may also stimulate mast cells in the gut, leading to reactions like bloating, diarrhea, or nausea.

2. Fillers & Additives – Some versions of cholestyramine contain dyes, sugar, artificial sweeteners (aspartame or saccharin), or preservatives, which can be mast cell triggers. A compounded, dye-free version is often better tolerated, and after I reacted to the orange-flavored and colored packets of CSM from my pharmacy, I switched to the plain CSM powder in the compounded version from my local Lake Elmo Compounding Pharmacy.

3. Binding of Nutrients & Medications – CSM binds to vitamins (A, D, E, K) and medications, which can lead to deficiencies over time. Vitamin deficiencies (especially B vitamins & magnesium) can worsen MCAS symptoms.

4. Detox Reactions (Biotoxin/Mold Illness Patients) – Some people take cholestyramine for mold toxicity or chronic inflammatory response syndrome (CIRS). If the body releases toxins too quickly, this can trigger mast cell flares (headaches, flushing, anxiety, gut issues).

How to Reduce the Risk of Reactions when taking CSM:

• Use a pure, compounded version (no dyes, sweeteners, or preservatives).
• Start with a very low dose (e.g., 1/4 packet or less).
• Support detox pathways (hydration, electrolytes, binders like activated charcoal if needed).
• Take vitamins separately (especially fat-soluble ones) so that they are not absorbed by the cholestyramine.

How it’s going

I’m taking the filler-free compounded cholestyramine now, and plan to continue it for three months. Then I’ll retest my mycotoxins to see if anything has changed in my bloodwork.

Sign up for the SSP!

The Safe and Sound Protocol (SSP) is a listening therapy based on Polyvagal Theory that helps heal nervous system regulation. Many people with MCAS have nervous system dysregulation stemming from infections, toxic exposures, concussions, and trauma. The SSP is an easy-to-use app where you listen to specially filtered music for 30 minutes each day for a 5-hour cycle. Studies show the SSP has a profound effect on mental health and chronic conditions

You can sign up for the SSP here!

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Disclaimer

The preceding material does not constitute medical advice. This information is for information purposes only and is not intended to be a substitute for professional medical advice, diagnosis, cure or treatment. Always seek advice from your medical doctor.