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, neck pain and the vagus nerve Mast cells in autoimmune disease Nature Mast Cell Activation Syndrome San Diego Naturopathic Doctor & IV Therapy Mast Cell Activation Syndrome: The Hidden Culprit Behind Mysterious Multi System Symptoms Dr. Jill Carnahan, MD