Mast cells are hypersensitive immune cells that release histamine and other inflammatory mediatorsoften in response to oxidative stress, environmental toxins, and immune imbalance. Many patients with MCAS have low levels of glutathione. Mast cell activation syndrome MEpedia Mast Cell Activation Syndrome: Symptoms, Causes, Diagnosis, and Treatment Mast Cells: MCAS, Genetics, and Solutions Mast Cell Activation Syndrome: A Primer for the Gastroenterologist Digestive Diseases and Sciences Springer Nature Link