7 Root Causes of Mast Cell Activation Syndrome

Mast cell activation syndrome (MCAS) is a condition in which immune cells called mast cells are excessively active, releasing large amounts of inflammatory chemicals like histamine.

Mast cells are found in many tissues and organs, including the gut, skin, and brain, just to name a few locations. (1, 2, 3) This is why MCAS can trigger many reactions throughout the body.

Sensitivities to heat, scents, chemicals, foods, supplements, and medications are common in people with MCAS. The various reactions triggered by MCAS can vastly reduce your quality of life. Back when I was dealing with severe MCAS symptoms, I could barely leave the house without having a reaction to heat, air pollution, or pollen in the air. It was a very challenging time.

The medical approach to MCAS involves using antihistamines and mast cell stabilizing medications. While these medications can be helpful, they do not address the root causes of MCAS.

In this article, I’ll discuss the top 7 root causes of mast cell activation syndrome and how you can address these root causes through nutrition, supplementation, detoxification, and lifestyle changes.

Please note that I am an affiliate for some of the products I’ve linked to in this post. If you click the link here and make a purchase, I may earn a commission at no extra cost to you.

The 7 Root Causes of Mast Cell Activation Syndrome

For most people with MCAS, some combination of the following 7 factors interacts to drive mast cell hyperreactivity. The top 7 root causes of mast cell activation syndrome include:

  1. Food sensitivities
  2. Chronic infections, such as Lyme disease and gut infections
  3. Mold exposure
  4. Nutritional deficiencies
  5. Hormone imbalances
  6. Limbic system hypersensitivity
  7. Sleep-disordered breathing and airway issues

Let’s discuss each of these root causes in turn.

infographic showing 7 root causes of mast cell activation syndrome

1.) Food Sensitivities

Many people with MCAS report food sensitivities. Sensitivities to high-histamine foods, high-oxalate foods, and high-salicylate foods are common. So why do certain types of foods trigger MCAS? It often comes down to the gut!

The gastrointestinal tract harbors the largest population of mast cells in the entire body! (4) Therefore, it makes sense that the foods you eat, which must pass through your gastrointestinal tract, can significantly affect mast cell activity and MCAS symptoms.

For example, if mast cells in your gut release large amounts of histamine, you may have a high level inside your gut. If your histamine “bucket” is already overflowing with gut-derived histamine, you may find yourself reacting to high-histamine foods because those foods are causing an even greater “overflow” of your histamine “bucket.”

Furthermore, if your gut is already inflamed and your microbiome imbalanced, food components such as oxalates and salicylates may exacerbate inflammatory mast cell activity.

Increased intestinal permeability, called “leaky gut,” is associated with heightened mast cell activity and food sensitivities. (5) Addressing the underlying causes of leaky gut, such as dysbiosis, and repairing leaky gut is essential for calming down mast cells and resolving food sensitivities.

Please note that while low-histamine, low-salicylate, and low-oxalate diets can be very helpful for getting MCAS under control, these diets are meant to be used over the short term. They are NOT meant to be used as long-term treatments for MCAS.

Eating a restrictive diet for an extended period can further disrupt your gut microbiome, cause nutrient deficiencies, and trigger food fear. I have experienced the adverse effects of an excessively restrictive diet for MCAS myself; at one point, I was down to just four foods I could eat for many months, and I know it ultimately did my health more harm than good.

For comprehensive guidance about what to eat to support MCAS recovery, check out my blog, “The Definitive Guide to the Mast Cell Activation Syndrome Diet.”

If you’re struggling with food sensitivities related to MCAS and feeling lost about nourishing your body, I’d love to help you in my nutrition practice!

While food reactions can often take up an overwhelming majority of your attention when you have MCAS, it’s crucial to recognize that food sensitivities are just one of the seven root causes of mast cell activation syndrome. Let’s discuss the other potential root causes next!

2.) Chronic Infections

For some people with MCAS, chronic infections are a mast cell trigger. Borrelia burgdorferi, one of the types of Borrelia bacteria that causes Lyme disease, has been shown to activate mast cells and trigger them to release histamine and other inflammatory signaling molecules. (6, 7)

Recall that the gastrointestinal system is full of mast cells… Well, it is also full of microorganisms that can produce histamine! For some people, infections in the gut are a significant trigger for mast cell hyperreactivity.

For example, the dysbiotic bacterium Klebsiella produces histamine and may provoke histamine overload and mast cell activation when it overgrows within the gut. In fact, Klebsiella aerogenes has been identified as a primary producer of histamine in the gut. (8)

An overgrowth of opportunistic yeast, such as Candida albicans, may also stimulate mast cell activity in the gut, playing a role in MCAS symptoms. (9)

Getting Candida overgrowth and other forms of gut dysbiosis under control can significantly improve your MCAS symptoms!

3.) Mold and Mycotoxin Exposure

Exposure to mold spores, mold fragments, and mycotoxins in water-damaged buildings can elicit MCAS. (10) Mold exposure played a significant role in the development of my MCAS symptoms.

How does mold affect mast cell activity? When your immune system is exposed to mold spores, the tiny reproductive cells of molds that waft through the air, it launches an inflammatory response that recruits mast cells.

In addition, some people who are exposed to mold and mycotoxins develop IgE antibodies to mycotoxins. IgE antibodies are proteins made by the immune system primarily involved in allergic reactions. IgE antibodies that target mycotoxins can bind to mast cells, causing rampant inflammation. (11)

If you’ve been exposed to mold, removing yourself from the mold-contaminated environment and detoxifying yourself from mold spore exposure, potential mold colonization, and mycotoxin toxicity is crucial for resolving MCAS.

4.) Nutritional Deficiencies

Your body requires many nutrients for proper immune system function, inflammation regulation, and histamine degradation. So if you’re deficient in one or more nutrients, those deficiencies could contribute to elevated mast cell activity.

For example, low levels of omega-3 fatty acids in the body can drive mast cell hyperreactivity. Conversely, replenishing omega-3 fatty acids through diet and supplementation may dampen mast cell reactivity. (12)

Many people with MCAS react to fish oil, so wild-caught flash-frozen seafood may be a better way for people with MCAS to bolster their omega-3 levels.

Low magnesium and vitamin C levels may also contribute to elevated histamine levels, impaired histamine breakdown, and MCAS symptoms. (13, 14)

In my practice, I often use the NutrEval test to assess my client’s nutritional status and ensure there are no nutritional gaps contributing to MCAS activity.

5.) Hormone Imbalances

Hormone imbalances may also contribute to MCAS. For example, high estrogen levels can trigger mast cells to release inflammatory signaling molecules. (15)

Factors that contribute to elevated estrogen include:

  • The intake of xenoestrogens through food, such as conventional dairy products, and personal care products, such as shampoo and lotions
  • Alcohol intake
  • Gut microbiome imbalances that inhibit estrogen breakdown
  • Impaired detoxification of estrogen
  • Hormonal birth control
  • Perimenopause

Elevated cortisol levels resulting from chronic stress may also trigger MCAS due to the effects of cortisol on mast cell activity.

6.) Limbic System Hypersensitivity

The limbic system is a portion of the brain responsible for learning and the fear response, among several other functions.

“Limbic system hypersensitivity” refers to a limbic system chronically in “red alert” mode and always on the lookout for potential threats. Limbic system hypersensitivity, also known as a chronic stress response, can often stem from an experience with chronic illness.

The chronic stress response releases neurochemicals that can activate mast cells. (16) Balancing limbic system hypersensitivity and supporting a more balanced stress response is vital for calming down mast cell activity.

One of the best ways to calm limbic system hypersensitivity is to engage in a brain retraining program.

Brain retraining programs are based on neuroplasticity, or the ability of neuronal networks to change through the processes of growth and reorganization.

For some people with MCAS, reactions to foods, supplements, and chemicals may stem from the brain creating unhealthy neural networks when chemical substances and odors are encountered in the environment. The formation of these neural networks creates a harmful form of neuroplasticity.

Conversely, brain retraining programs are designed to help the brain utilize different, healthier neural networks, eventually turning the negative associations between various chemical substances and odors into “neutral” associations. Over time, this “rewiring” process can alleviate MCAS symptoms.

There are many brain retraining programs on the market directed towards individuals with chronic illnesses such as MCAS, mold illness, and chronic Lyme disease. These programs incorporate mindfulness practices, visualization techniques, language, and body movements to rewire the maladapted stress response and, ultimately, desensitize the body to chemicals.

Brain retraining programs often require a commitment of at least several months before significant, consistent changes can be observed in symptoms of MCAS.

A few of my favorite brain retraining programs include Vital-Side, DNRS, and the Gupta Program.

7.) Sleep-Disordered Breathing and Airway Issues

Sleep-disordered breathing refers to a broad spectrum of sleep-related conditions, including upper airway resistance and sleep apnea, that affect not only sleep quality but also numerous other aspects of health, including metabolic health.

Sleep-disordered breathing and airway issues can cause hypoxia, a lack of oxygen in the body’s tissues. Hypoxia, in turn, can cause mast cell degranulation and a release of inflammatory signaling molecules from mast cells. (17)

In my experience, most people with MCAS are entirely unaware (myself included, at one point!) of the critical role of sleep-disordered breathing and airway issues on hypoxia and MCAS activity.

Importantly, you don’t have to be a heavy snorer to have sleep-disordered breathing and airway issues. Some sneaky signs of sleep-disordered breathing and airway issues include:

  • Insomnia – difficulty either falling asleep or staying asleep throughout the night
  • Chronic fatigue
  • Mouth breathing while sleeping
  • Elevated blood sugar, despite eating well and exercising
  • Air hunger

If you suspect you may be dealing with sleep-disordered breathing or airway issues, I recommend consulting a sleep dentist. The American Academy of Dental Sleep Medicine provides a database in which you can find a sleep dentistry specialist. 

It is also wise for almost everybody to do a sleep study at least once. The Sleep Image ring provides a non-invasive way to do a sleep study at home. I’ve used it myself, and it helped me identify moderate sleep apnea.

The Bottom Line on the 7 Root Causes of Mast Cell Activation Syndrome

MCAS is a complex condition with many potential root causes. Identifying and addressing the root causes that are relevant for you will help you more effectively resolve MCAS and get your symptoms under control so you can get back to living your life!

Do you need personalized functional healthcare support in your MCAS healing journey? I’d love to work with you one-on-one in my practice! If you’re ready to start, book your free discovery call to learn more about how I can help!

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top