Mast Cell Activation Syndrome

Mast cell activation syndrome (MCAS) is a condition wherein the body's mast cells release chemicals in response to triggers. This can cause an allergic-type reaction with hives, GI distress, wheezing, and low blood pressure. Mast cells are allergy cells and sometimes behave abnormally. MCAS causes repeated episodes of allergic symptoms, sometimes severe, in response to normal everyday foods or substances. Certain tests can be performed on patients with these symptoms to determine if MCAS is the cause. Often antihistamines can help with symptoms. Patients can receive diagnosis and care from an allergy specialist. 

https://www.aaaai.org/conditions-treatments/related-conditions/mcas