MCAS (Mast Cell Activation Syndrome)

by Lucia Stansbie

MCAS (Mast Cell Activation Syndrome) is a condition in which mast cells—a type of immune cell involved in allergic and inflammatory responses—become overactive and release excessive amounts of chemical mediators (such as histamine, prostaglandins, leukotrienes) inappropriately and repeatedly.

A hallmark of the condition is its multi-system involvement, meaning that symptoms typically affect several parts of the body at the same time. Individuals may experience skin manifestations such as flushing or itching, gastrointestinal disturbances like abdominal pain or diarrhoea, cardiovascular symptoms including tachycardia or low blood pressure, as well as neurological or respiratory issues.

These symptoms are mediated by the release of substances such as histamine, tryptase, prostaglandins, and leukotrienes, which contribute to inflammation and hypersensitivity reactions throughout the body.

Another defining feature of MCAS is its fluctuating and episodic nature. Symptoms tend to come and go, often in flares that can be triggered by a wide range of factors, including certain foods, stress, infections, environmental exposures, or changes in temperature.