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 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: A Primer for the Gastroenterologist Digestive Diseases and Sciences Springer Nature Link AAAAI Mast Cell Disorders Committee Work Group Report: Mast cell activation syndrome (MCAS) diagnosis and management Journal of Allergy and Clinical Immunology Mast cell activation syndrome, neck pain and the vagus nerve