MCAS is a condition in which mast cells in the body inappropriately activate and release substances. This causes a wide range of symptoms that often mimic allergic reactions. Examples include skin complaints such as redness and itching, circulatory problems such as low blood pressure and fainting, gastrointestinal complaints such as abdominal cramps and diarrhea, respiratory complaints such as nasal congestion or itching, and other symptoms such as fatigue, difficulty concentrating, and a general feeling of being unwell. View our page about MCAS for more information.
