Mast Cell Activation Syndrome and Its Impact on the Lymphatics Mast Cell Activation Syndrome (MCAS) Dr. Todd Maderis Why Your Body Overreacts to Pollen (And What Actually Works to Support Seeking Health 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. Dr. Michael Ruscio on SIBO and gut health as drivers of MCAS: Mast Cell Matters with