Mast Cell Activation Syndrome (MCAS) is a condition in which mast cells release excessive amounts of chemical messengers, such as histamine, inflammatory cytokines and prostaglandins, even when there is no significant threat. This can cause a wide range of symptoms, including flushing, itching, headaches, digestive problems, nasal congestion, dizziness and reactions to foods, medications or environmental triggers. MCAS is complex and should be assessed by a qualified healthcare practitioner, as many other conditions can cause similar symptoms.