Mast cell activation syndrome, neck pain and the vagus nerve Did you know one single mast cell can release chemicals that affect your skin, gut, heart, brain, and immune system all at once? That's why MCAS can feel so overwhelming, the 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. Ways to Address Perinatal Mast Cell Activation and Focal Brain Inflammation, including Response to SARS CoV 2, in Autism Spectrum Disorder