Mast Cell Activatation Syndrome

Mast Cell Activation Syndrome (MCAS) and Histamine Intolerance are increasingly recognized in integrative medicine as contributing factors to various chronic health issues and I will explain the symptoms and possible causes. It is important to understand the clinical presentation and the root cause in order to provide the best chance of healing.

Understanding MCAS

MCAS occurs when mast cells become excessively active and infiltrate different organs, leading to widespread inflammation. It is categorized into three types:

Primary MCAS: Caused by a genetic mutation (KIT gene) leading to mast cell overproduction, often diagnosed through a bone marrow biopsy. This is known as Mastocytosis and is rare, affecting about 1 in 10,000 people.
Secondary MCAS: Mast cells exist in normal numbers but overreact to triggers such as allergens, infections, or chronic inflammatory conditions.
Idiopathic MCAS: There is no identifiable cause, yet the individual experiences symptoms like anaphylaxis, swelling, hives, and other systemic reactions.

Where Are Mast Cells Located?

Mast cells are distributed throughout the body but are most concentrated in the skin, respiratory tract, and gastrointestinal lining, where they help defend against external irritants.

How Mast Cells Contribute to Symptoms

Mast cells release inflammatory mediators like histamine, tryptase, and cytokines, which trigger symptoms. Tryptase is a key marker used in testing for MCAS.

Symptoms of MCAS

MCAS can affect nearly every system in the body:

Cardiovascular: High blood pressure, fainting, dizziness, rapid heart rate
Skin: Flushing, hives, itching, swelling
Digestive: Abdominal cramps, diarrhea, acid reflux, nausea, vomiting
Musculoskeletal: Joint pain, fibromyalgia, osteoporosis
Neurologic: Anxiety, depression, migraines, insomnia, difficulty concentrating
Respiratory: Nasal congestion, sneezing, wheezing, asthma, throat swelling
Reproductive/Urinary: Painful urination, frequent urination, menstrual irregularities
Systemic: Fatigue, unexplained weight loss

Histamine Intolerance vs. MCAS

Histamine Intolerance occurs when the body accumulates excess histamine beyond its ability to break it down. This condition affects approximately 1% of the population and shares symptoms with MCAS. Causes include:

Increased histamine intake from foods
Excess histamine release from mast cells
Reduced histamine breakdown due to deficiencies in the enzymes DAO (diamine oxidase) or HNMT (histamine N-methyltransferase)

High-Histamine Foods to Avoid

Fermented foods: Kombucha, sauerkraut, wine, vinegar
Aged cheeses
Processed meats: Cured, smoked, marinated, or canned meats
Certain vegetables & fruits
Other sources: Chocolate, carob, soy products

Diagnosing MCAS and Histamine Intolerance

Diagnosing these conditions involves a comprehensive assessment, including:

Food sensitivity testing
Diet tracking
Gut microbiome analysis (stool test, SIBO test, fungal assessment)
Toxin exposure evaluation (mold, heavy metals, chemicals)
POTS (Postural Orthostatic Tachycardia Syndrome) assessment
Lab tests: Histamine levels, baseline tryptase, and post-meal tryptase testing
Genetic SNP testing

Treatment Approaches

A low-histamine diet is the primary dietary intervention, along with:

Nutritional support: Vitamin C, bioflavonoids, magnesium, copper, and B vitamins
Avoiding leftovers (histamine increases in aged foods unless frozen)
Supplements: DAO enzyme (though often ineffective), antioxidants, and fish oil

Medications for Symptom Management

These medications provide symptoms relief and are important part of the treatment phase, however, they are not longterm solution or cure of MCAS.

H1 blockers: Cetirizine, loratadine, fexofenadine, hydroxyzine
H2 blockers: Famotidine
Leukotriene inhibitors: Montelukast (Singulair)
Mast cell stabilizers: Cromolyn sodium, ketotifen
Low-dose naltrexone for immune modulation
Steroids (rare use): Budesonide, dexamethasone for severe cases

Conclusion

Both MCAS and histamine intolerance are becoming increasingly recognized. With proper diagnosis, personalized treatment, and lifestyle adjustments, symptom stabilization and long-term healing are possible.