What is it?

Mast cell activation syndrome (MCAS) is a condition in which mast cells, which are a part of the immune system, release too much of the substance inside it. Mast cells are found in the bone marrow and respond to stress or danger by releasing mediators that cause inflammation. In MCAS, the body releases too many mediators too often. The reason for these conditions is unknown, but it may be due to a genetic factor. Risk factors include allergic-type triggers, drug-induced triggers, anxiety, pain, exercise, infection, smells, hormonal changes and mast cell hyperplasia due to chronic infections or malignancies.

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Signs & symptoms

Mast cell activation syndrome symptoms vary because it can present in any body system. Usually, it affects the skin, nervous system, heart and gastrointestinal tract. Symptoms may include itching skin, flushing, sweating, watering or itching eyes and nose, swelling of the lips or throat, difficulty breathing, low blood pressure, rapid heart rate, cramping, diarrhea, nausea, abdominal pain, headache, dizziness, confusion, and fatigue.


Mast cell activation syndrome is diagnosed when the symptoms affect at least two body systems, when there are high levels of mediators markers in the blood or urine, and when medications that block the mediators help the symptoms.


Mast cell activation syndrome treatment includes medications such as antihistamines, mast cell stabilizers, antileukotrienes, and corticosteroids.

☝️ This is not a substitute for professional medical advice. Please consult with your physician before making any medical decision.

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