For many people living with endometriosis, the pain, inflammation, and fatigue don’t tell the whole story. A growing number of patients are discovering that their symptoms overlap with another condition: Mast Cell Activation Syndrome (MCAS) . While research is still emerging, the relationship between Endo and MCAS is becoming too significant to ignore. What Is MCAS? Mast Cell Activation Syndrome happens when mast cells , immune cells involved in allergic and inflammatory resp