Diamine oxidase (DAO) is the main enzyme responsible for breaking down histamine in the digestive tract. DAO deficiency - whether genetic or caused by gut inflammation or dysbiosis - is the primary driver of histamine intolerance (HIT). When DAO activity is low histamine from food and gut bacteria accumulates triggering symptoms including headaches, skin flushing, bloating, diarrhea, and nasal congestion. Supporting gut health can improve DAO function by reducing intestinal inflammation.
