Mast cell activation syndrome (MCAS) occurs when the mast cells in your body release too much of the substances inside them at the wrong times. Mast cells are part of your immune system. They’re found in your bone marrow and around the blood vessels in your body. When you’re exposed to stress or danger, your mast calls respond by releasing substances called mediators. Mediators cause inflammation, which helps your body heal from an injury or infection. This same response happens during an allergic reaction. Your mast cells release mediators to remove the thing you’re allergic to. For example, if you’re allergic to pollen, your mast cells release a mediator called histamine, which makes you sneeze to get rid of the pollen. If you have MCAS, your mast cells release mediators too frequently and too often. It’s different from another mast cell disorder called mastocytosis, which happens when your body makes too many mast cells.
Explore More