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Mast Cell Activation Syndrome (MCAS)
Mast Cell Activation Syndrome (MCAS) is a condition where mast cells—part of the immune system—inappropriately release excessive amounts of chemical mediators like histamine, leukotrienes, and cytokines. This causes systemic, allergic-like symptoms across multiple organ systems, often without a clear allergic trigger.
Common Symptoms
Skin: Hives, flushing, itching, sweating
Gastrointestinal: Nausea, vomiting, diarrhea, abdominal cramping
Cardiovascular: Rapid heart rate, low blood pressure, fainting
Respiratory: Wheezing, shortness of breath, nasal congestion
Neurological: Brain fog, headaches, fatigue, anxiety
Causes & Triggers
- Environmental triggers (mold, strong odors, temperature changes)
- Food and beverages (high histamine foods, alcohol)
- Stress (physical and emotional)
- Infections and viruses
- Medications and excipients
Diagnosis
Diagnosis typically involves a clinical evaluation of symptoms across at least two organ systems, laboratory evidence of elevated mast cell mediators (e.g., serum tryptase, 24-hour urine histamine, prostaglandins) during a flare, and a positive response to medications that block mast cell mediators.
Treatment Approaches
Identifying and avoiding triggers
H1 and H2 antihistamines (e.g., Cetirizine, Famotidine)
Mast cell stabilizers (e.g., Cromolyn sodium, Ketotifen)
Leukotriene inhibitors (e.g., Montelukast)
Dietary modifications (low histamine diet)
Research & Sources
Mast cell activation syndrome: Proposed diagnostic criteria
Journal of Allergy and Clinical ImmunologyView Source
Diagnosis of mast cell activation syndrome: a global "consensus-2"
DiagnosisView Source