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. Understanding MCAS and Hypermobility: Overlapping Conditions Mast cell activation syndrome, neck pain and the vagus nerve Social Security Disability for Mast Cell Activation Syndrome The Bishop Law Firm