Mast cell activation syndrome (MCAS) is a complex and often misunderstood disorder of the immune system that occurs when mast cells — a type of white blood cell — trigger an excessive inflammatory response.

MCAS can cause a range of symptoms, including skin rashes, itching, flushing, bloating, constipation or diarrhea, difficulty breathing, fatigue, headaches, joint and muscle pain, and neurological symptoms. It often makes people hypersensitive to foods they never had a problem eating in the past.

Based on their symptoms, patients with MCAS are often diagnosed as having allergies, asthma, myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), postural tachycardia syndrome (POTS), an inflammatory bowel disease (such as Crohn’s or ulcerative colitis), or another medical condition. Meanwhile, their underlying MCAS, which is the root cause of their symptoms, remains undiagnosed and untreated.

Illustration of Mast Cell

If you’re experiencing the symptoms I described or you’ve been diagnosed as having one of the conditions I mentioned, you’ve probably been prescribed medication to alleviate your symptoms. Medication for symptom relief may be effective to some degree for a period of time, but it doesn’t fully address the underlying issue. As a result, you’re likely to continue to suffer.

Through this post, I’m hoping to increase awareness of mast cell activation syndrome, so more patients can get the right diagnosis and effective treatment.

Identifying Your Triggers

When they function properly, your mast cells play an important role in protecting your body against pathogens, such as infectious bacteria and viruses. When these cells perceive a potential threat, they release chemical mediators — including histamine — to launch a rapid immune response intended to destroy and eliminate the pathogen.

However, when these cells become overly sensitive, they release chemical mediators in response to non-threatening triggers. Sometimes, they release too much. Triggers vary among individuals and may include the following:

  • Heavy metals
  • Alcohol
  • Mold/fungus
  • An allergen
  • Insect bites
  • Chemicals in personal products
  • Certain medications
  • Emotional stress
  • Exposure to sunlight
  • Certain food items (which vary among individuals)
  • Extreme temperatures (hot or cold)
  • Certain fragrances (such as perfume or cologne)
  • Infection (bacterial, viral, or fungal)

There are several factors that make mast cells overly sensitive, contributing to the development of MCAS, including:

  • Food triggers
  • Genetic susceptibilities
  • Head trauma
  • Hormone imbalances
  • Hypoxia (low oxygen)
  • Infections
  • Nutritional deficiencies
  • Stress
  • Toxicity

MCAS in My Clinical Practice

In my clinical practice, I have observed a link between patients with mast cell activation syndrome and environmentally acquired illness (EAI) — typically from exposure to mold through water-damaged buildings and the subsequent exposure to volatile organic compounds (VOCs), microorganisms, and mold toxins.

In fact, MCAS and EAI share many of the same symptoms. It seems that chronic exposure to toxic mold and other environmental irritants makes mast cells overly sensitive to a variety of triggers.

Many of the people I treat have had MCAS for many years and are often treating it with over-the-counter or prescription medications such as antihistamines and decongestants. However, their symptoms persist because the underlying causes remain undiagnosed and untreated.

Some of my patients have symptoms of mast cell activation and ME/CFS, suggesting that these two conditions may be related. Symptoms of ME/CFS include the following:

  • Fatigue
  • Exercise intolerance — extreme exhaustion after physical or mental exercise
  • Cognitive difficulties — impaired memory or thinking
  • Dizziness that worsens when standing up from a sitting or prone position
  • Muscle or joint pain
  • Feeling tired after a full night’s sleep

Note that many of these symptoms are also characteristic of postural tachycardia syndrome (POTS). In patients with ME/CFS and POTS, the mast cells appear to trigger the sympathetic nervous system to overreact to small events, like standing or exercising.

Some patients who say they feel worse with exercise are actually having exercise-induced mast cell activation, which, in a way is like being allergic to exercise. That’s not normal. Exercise should make you feel better, not worse.

Diagnosing MCAS

Diagnosing MCAS is challenging. Labs are often normal for the typical inflammatory markers, complete blood counts, and metabolic panels, making diagnosis difficult for clinicians who are not paying attention to clinical diagnostic signs. For example, the patient may have low blood pressure, which is often ignored by the doctor and considered as normal.

Diagnosing MCAS involves running lab tests to check for elevated levels of certain mast cell mediators in the blood or urine, including tryptase, N-methylhistamine, 11B -Prostaglandin F2α (11B-PGF2α), and Leukotriene E4 (LTE4). However, unless you’re currently experiencing an episode, levels of these mast cell mediators may be normal.

In other words, testing is great if it confirms a suspected case of MCAS, but testing alone can’t rule it out. Regardless of what the test results show, a deeper clinical examination is needed to identify each patient’s triggers and identify what could possibly be causing the overactivation of mast cells. This deeper examination focuses on the following factors:

  • Food intolerances: These can be identified through lab testing or an elimination diet.
  • Change in digestion or bowel movements: Symptoms of MCAS can mimic those of small intestinal bacterial overgrowth (SIBO), including abdominal pain, bloating, and diarrhea.
  • Mold toxins: A simple urine test can check for the presence of mold toxins — the most common underlying cause of MCAS.
  • Environmental toxins and heavy metals: Excessive activation of the immune system may result from exposure to heavy metals and environmental contaminants. Typical origins include lead, dental amalgams’ mercury, and organophosphates found in fertilizers. Carefully targeted lab tests, based on the patient’s symptoms and history, can help identify the heavy metals and toxins causing the problem.
  • Genetic susceptibilities: For example, some people don’t produce enough diamine oxidase (DAO) — a chemical that breaks down histamine — and some people’s ability to detox is impaired.
  • Head trauma and stress: MCAS has been connected to brain injury, stress, post-traumatic stress disorder (PTSD), and Alzheimer’s disease.

Treating MCAS

Typically, traditional approaches to address mast cell activation syndrome include the utilization of pharmaceutical and non-prescription drugs to relieve symptoms. Such medications may include the following:

  • Epinephrine (such as an EpiPen) for severe reactions
  • Diphenhydramine (Benadryl), hydroxyzine (Vistaril), and other first-generation H1 blockers
  • Loratadine (Claritin), cetirizine (Zyrtec), fexofenadine (Allegra), and other second-generation H1 blockers
  • Ranitidine (Zantac), famotidine (Pepcid), and other H2 blockers
  • Aspirin, to block production of prostaglandin D2 and reduce flushing. However, aspirin can also trigger episodes in many patients.
  • Montelukast (Singulair) and zafirlukast (Accolate) to block the effects of leukotriene C4 (LTC4), and zileuton (Zyflo) to block LTC4 production

While these medications can be very helpful for dialing down the immune response and alleviating symptoms, they often stop short of addressing the root cause.

MCAS is most commonly related to mold exposure in a water-damaged building — usually the current or a previous residence. If the exposure is current, having the home tested and conducting mold remediation (if necessary) is a key first step. Hire a reputable mold remediation specialist; trying to do it yourself will increase your exposure and may not be effective.

I work closely with each of my patients to develop a personalized treatment plan that addresses the individual’s unique symptoms, triggers, and underlying causes. Treatment may include:

  • Natural supplements to reduce mast cell activation
  • Identification and avoidance of triggers
  • A personalized gastrointestinal repair protocol to restore balance to the gut microbiome (the beneficial bacteria and other microorganisms living in the intestinal tract) and repair any damage to the intestinal lining
  • A personalized detox protocol to support the body’s natural ability to detoxify itself
  • Anti-inflammatory nutrients to reduce inflammation

If you are experiencing symptoms of mast cell activation syndrome, whether those symptoms are life-threatening or not, I encourage you to schedule a thorough evaluation with a functional and integrative medical practice.

A comprehensive assessment involves a meticulous review of both your medical background and family medical history, coupled with specific laboratory tests to assess chemical mediators, deficiencies in nutrition, genetic predispositions, concealed infections, toxins, allergic reactions, food intolerances, sensitivities, and related factors.

When it comes to your health and wellbeing, I recommend that you refuse to accept treatments that merely mask symptoms. Insist instead on a thorough and customized plan of care that identifies and resolves the underlying causes of your symptoms.

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Frequently Asked Questions about Diagnosing and Treating Mast Cell Activation Syndrome

What specific dietary changes can help manage symptoms of MCAS?

For managing symptoms of Mast Cell Activation Syndrome (MCAS), making dietary changes that focus on reducing intake of foods high in histamines and other triggers can be beneficial. This involves identifying and avoiding specific foods that worsen your symptoms. A qualified healthcare provider — one with the latest knowledge and training for diagnosing and treating Mast Cell Activation Syndrome — will make specific recommendations about dietary changes that will help you manage your symptoms.

How does I find a healthcare provider experienced in treating Mast Cell Activation Syndrome, considering its complexity and the need for personalized care?

Finding a healthcare provider with experience in treating Mast Cell Activation Syndrome (MCAS) can be challenging due to the condition’s complexity. It’s often recommended to consult with patient advocacy groups or networks specializing in MCAS to get referrals to knowledgeable practitioners. In Tampa, Florida, PROVOKE Health offers diagnosis and treatment for Mast Cell Activation Syndrome.

Can lifestyle changes alone be sufficient to manage Mast Cell Activation Syndrome, or is medication always necessary?

While lifestyle modifications, including avoiding known triggers and stress management, are important in managing Mast Cell Activation Syndrome (MCAS), they might not be sufficient on their own. Many patients with MCAS may also require medication to control their symptoms effectively and prevent severe allergic reactions.

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About the Author: Dr. Matt Lewis, D.C., DACBN, CFMP®, specializes in diagnosing and treating the underlying causes of the symptoms related to chronic and unexplained illness through nutrition, lifestyle, chiropractic, and other natural approaches to whole-health healing in Tampa, Fla. Dr. Lewis has 20 years of experience practicing nutritional and holistic medicine. He earned his B.S. in Biology from Shenandoah University, his Doctorate in Chiropractic from Life University, his Diplomate status in Clinical Nutrition from the American Clinical Board of Nutrition, his CFMP from Functional Medicine University, and his certification as a Digestive Health Specialist (DHS) through the Food Enzyme Institute. Dr. Lewis’ passion for health and wellness stems from his own personal experience. With a family history of autoimmune conditions and diabetes, and his own lab tests showing his genetic susceptibility to Hashimoto’s thyroiditis (autoimmune thyroid), Dr. Lewis has learned how to restore his own health and vigor to prevent the onset of these and other illnesses and live an incredibly active life. Through this process, he acquired a deeper understanding of health and wellness, which he now offers his patients in Tampa and elsewhere.

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Dr. Matt