Mast Cell Activation Syndrome (MCAS): Causes, Symptoms & Functional Treatment

Have you ever experienced mysterious allergy-like symptoms—rashes, brain fog, flushing, or stomach pain—with no clear trigger? You might have been told it's “just stress” or given a catch-all diagnosis like IBS or anxiety. But these diverse, seemingly disconnected symptoms might have a unifying root: Mast Cell Activation Syndrome (MCAS).

MCAS is a complex, underdiagnosed condition in which mast cells—key players in the immune system—become hyperactive and release inflammatory mediators inappropriately, even without a traditional allergic trigger. The result? Chronic symptoms that can affect nearly every system in the body.

In this comprehensive guide, we’ll explore what MCAS is, what causes it, how it’s diagnosed, and how a functional medicine approach can help restore balance, calm inflammation, and support long-term healing.

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What Are Mast Cells?

Mast cells are a type of white blood cell that live in connective tissue, especially near blood vessels, skin, lungs, and the gastrointestinal tract. They play a key role in:

• Allergic reactions

• Wound healing

• Immune defense against pathogens

• Regulating inflammation

When activated, mast cells release granules filled with bioactive substances, including:

• Histamine

• Tryptase

• Prostaglandins

• Leukotrienes

• Cytokines

This process is called degranulation—and in normal situations (e.g., in response to an insect sting or parasite), it's protective. But in MCAS, this activation happens inappropriately, excessively, and often chronically.

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What Is Mast Cell Activation Syndrome (MCAS)?

MCAS is a chronic condition in which mast cells release too many chemical mediators, leading to multisystem inflammation, hypersensitivity, and dysfunction. Unlike classic mastocytosis (where mast cells are overproduced), in MCAS the mast cell count is normal, but their behavior is dysregulated.

This condition is estimated to affect up to 17% of the general population, but due to its broad and confusing symptom profile, it’s frequently missed.

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Symptoms of MCAS

MCAS symptoms vary depending on which organ systems are affected. Here’s how it may present:

🧠 Neurological & Cognitive

• Brain fog

• Headaches or migraines

• Anxiety or panic attacks

• Insomnia

• Light or sound sensitivity

• Dizziness or balance problems

🌬 Respiratory

• Shortness of breath

• Asthma-like symptoms

• Nasal congestion

• Frequent throat clearing

• Chronic cough

💩 Gastrointestinal

• Bloating

• Nausea or vomiting

• Diarrhea or constipation

• Acid reflux

• Abdominal pain

• Food intolerances

💓 Cardiovascular

• Heart palpitations

• Low blood pressure

• Flushing or facial redness

• Dizziness on standing (POTS)

🦴 Musculoskeletal

• Joint pain

• Muscle aches

• Bone pain

🧴 Dermatological

• Hives

• Itching without rash

• Rashes or eczema

• Dermatographia (skin writing)

🔁 Systemic

• Fatigue

• Temperature dysregulation

• Sensitivity to smells, chemicals, or stress

• Reactions to medications, supplements, or anesthesia

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Common Triggers of Mast Cell Degranulation

People with MCAS often react to otherwise harmless stimuli. Common triggers include:

• Foods: histamine-rich foods (aged cheese, alcohol), fermented foods, shellfish

• Temperature extremes

• Exercise or physical pressure

• Environmental toxins

• Mold and mycotoxins

• Emotional stress

• Infections (viral, bacterial, parasitic)

• Medications: NSAIDs, opioids, certain anesthetics

• Hormonal shifts (e.g., during menstruation)

Understanding personal triggers is essential to managing MCAS successfully.

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Conditions Commonly Associated with MCAS

MCAS rarely occurs in isolation. It is often seen alongside:

• Ehlers-Danlos Syndrome (EDS)

• POTS (Postural Orthostatic Tachycardia Syndrome)

• Small Intestinal Bacterial Overgrowth (SIBO)

• Mold illness (CIRS)

• Lyme disease and co-infections

• Long COVID or post-viral syndromes

• Autoimmune disease (e.g., Hashimoto’s, lupus)

• Histamine intolerance

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Diagnosing MCAS

MCAS is a clinical diagnosis, supported by lab testing. Unfortunately, there is no single gold-standard test, and lab markers can fluctuate.

Diagnostic Criteria (Adapted from consensus guidelines):

1. Chronic multisystem symptoms consistent with mast cell activation

2. Evidence of elevated mast cell mediators (during flare or baseline), such as:

   • Serum tryptase

   • Plasma histamine

   • Chromogranin A

   • Urinary N-methylhistamine

   • Urinary prostaglandin D2 or F2α

3. Improvement with medications that block mast cell activity (e.g., antihistamines, cromolyn sodium)

Testing is most accurate when done during or soon after a flare, and samples often need to be chilled and analyzed at specialized labs.

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Functional Medicine Approach to MCAS

In functional medicine, we don’t just suppress symptoms—we look for why the mast cells are overreacting and what triggers can be removed, calmed, or modulated. Here's a comprehensive strategy:

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Step 1: Remove Triggers

Start with a low-histamine, low-inflammatory diet:

Avoid:

• Aged cheese, smoked meats, wine, vinegar, fermented foods

• Leftovers (histamine increases with time)

• Tomatoes, spinach, avocado, citrus

• Shellfish

• Chocolate

• Alcohol

• Food dyes, preservatives (especially benzoates)

Also Eliminate:

• Mold exposure (test the home if needed)

• EMF overexposure in sensitive individuals

• NSAIDs and other mast cell-activating medications (under supervision)

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Step 2: Heal the Gut and Support the Microbiome

The gut is a major mast cell hub, and healing the gut is essential. Focus on:

• BPC-157 – Peptide that repairs intestinal lining

• Immuno-30 – Binds and removes food toxins, supports immune modulation

• Curcumin Complex – Stabilizes mast cells and reduces cytokine expression

• Omega 1300 – Resolvins that reduce inflammation

• Mega Sporebiotic – Spore-based probiotic to restore microbiome balance

• Zinc carnosine & L-glutamine – Strengthen gut barrier

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Step 3: Calm the Immune System

Use natural and targeted agents to stabilize mast cells and reduce reactivity.

Key Natural Stabilizers:

• AllerFx – Quercetin and luteolin blend that reduces histamine

• Vitamin C – Depletes histamine and supports antioxidant defense

• DAO – Helps degrade histamine from food

• B12 & Folate – Supports methylation and detoxification

• Mag Glycinate – Nervous system support

Peptides:

• KPV peptide – Strong anti-inflammatory, reduces IL-6, TNF-α

• TB-500 – Promotes tissue repair and immune modulation

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Step 4: Address Root Causes

Uncover and treat underlying conditions contributing to MCAS:

• Mold/mycotoxins → Use mycotoxin testing + binders (e.g., charcoal, chlorella)

• Chronic infections → Treat with targeted antimicrobials or peptides

• Heavy metals → Test and chelate with supervision

• Hormone imbalance → Normalize estrogen, cortisol, and thyroid function

• Dysautonomia or POTS → Electrolytes, vagal support, beta blockers if needed

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Step 5: Nervous System Regulation

Mast cells are influenced by neuropeptides and stress hormones, so calming the nervous system is vital.

Try:

• Vagal nerve stimulation (gargling, humming, cold exposure)

• Breathwork and HRV training

• EMDR or somatic therapy

• Gentle movement (yoga, stretching)

• Low-dose naltrexone (LDN) under physician guidance

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Medications Often Used for MCAS

While functional medicine focuses on the root cause, medications may be helpful short-term or during flares:

• H1 blockers: loratadine, cetirizine, hydroxyzine

• H2 blockers: famotidine, ranitidine

• Mast cell stabilizers: cromolyn sodium, ketotifen

• Leukotriene inhibitors: montelukast

• Aspirin (in salicylate-tolerant individuals): blocks prostaglandins

• LDN (Low-Dose Naltrexone): modulates immune response

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Living with MCAS: Practical Tips

• Keep a symptom diary to track flares and exposures

• Store and consume fresh food—histamine builds up in leftovers

• Use HEPA filters in home and bedroom

• Avoid scented products and chemical cleaners

• Communicate MCAS with medical providers—especially before surgery or dental work

• Build a flare kit (antihistamines, electrolytes, DAO, KPV, Cromolyn)

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Final Thoughts

Mast Cell Activation Syndrome is complex—but not impossible to treat. By removing triggers, restoring gut integrity, calming the immune response, and addressing root causes, many patients can dramatically reduce symptoms and reclaim their quality of life.

MCAS isn’t just “in your head.” It’s a real and treatable condition—and with a functional medicine lens, it becomes a solvable puzzle.

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Ready to Get to the Root of Your Symptoms?

At Revolution Health & Wellness, we use advanced testing, peptide therapy, precision supplementation, and personalized care plans to help patients with MCAS regain control of their lives.

📞 Contact us today to schedule a consultation and begin your healing journey.

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References

1. Afrin LB. (2016). Never Bet Against Occam: Mast Cell Activation Disease and the Modern Epidemics of Chronic Illness and Medical Complexity.

2. Molderings GJ, et al. (2011). The idiopathic mast cell activation syndrome. Immunol Allergy Clin North Am.

3. Weinstock LB, et al. (2020). Mast Cell Activation Syndrome: A Primer for the Gastroenterologist. Am J Gastroenterol.

4. Theoharides TC, et al. (2015). Mast cells and inflammation. Biochim Biophys Acta.

5. Chelombitko MA, et al. (2016). Regulation of mast cell functions by neurotransmitters. Biochem Biophys Res Commun.