Update on Mast Cell Activation Syndrome (MCAS) Black & Kletz Allergy Mast Cell Activation Syndrome and Its Impact on the Lymphatics Mast Cell Activation Syndrome: The Hidden Culprit Behind Mysterious Multi System Symptoms Dr. Jill Carnahan, MD How Mycotoxins Trigger Mast Cell Activation and Brain Inflammation 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.