Information about Mast Cell Activation Syndrome, MCAS Mast Cell Activation Syndrome: A Primer for the Gastroenterologist Digestive Diseases and Sciences Springer Nature Link Mast Cell Activation Syndrome Effects of cancer induced cachexia and administration of l glutathione on the intestinal mucosa in rat Amino Acids Springer Nature Link 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.