By Linda-Anne Kahn CLT-LANA, NCBTMB, CDT, CHNC This is a 9-minute read. Mast cell activation syndrome (MCAS) is found in 1 in 10,000 to 20,000 people. It involves severe allergic reactions due to the activation of antibodies on the body’s mast cell surfaces, which are found throughout the skin, blood vessels, ...