Histamine intolerance generally results from a deficiency in the enzyme DAO, which is responsible for breaking down histamine in the gastrointestinal tract. Other causes include impaired histamine-N-methyltransferase activity, genetic polymorphisms affecting enzyme function, and increased histamine load from the diet. Certain medications, alcohol, and gastrointestinal disorders like celiac disease and inflammatory bowel disease can also impair histamine breakdown.
