Many challenging medical conditions defy treatment and challenge clinicians to come up with innovative solutions—Chronic Fatigue Syndrome, fibromyalgia, Lyme Disease, Multiple Chemical Sensitivity (MCS), Ehlers-Danlos Syndrome (EDS) and autoimmune conditions; add now the growing burden of patients with Long Covid and vaccine injury. Dr. Tania Dempsey specializes in treating these complicated chronic disorders. She has embraced and advanced a new paradigm based on addressing Mast Cell Activation Syndrome (MCAS). What is MCAS? How is it differentiated from ordinary allergies, and why are its symptoms so pervasive? What are its causes and triggers? What role for low-histamine diets? Antihistamines? Other novel medications? What nutritional supplements can facilitate its resolution? How does recognition of the contribution of MCAS facilitate treatment of patients suffering from Long Covid and vaccine injuries?