was ist histamin — which blood markers matter?

Histamine is a biogenic amine acting as a neurotransmitter and immune mediator, also found in foods. In suspected histamine intolerance (e.g., DAO deficiency, mast cell disorders), blood markers such as serum histamine, diamine oxidase (DAO) activity, and tryptase may be considered. However, direct histamine measurement is unreliable due to rapid degradation. Clinically, serum DAO activity is more common: values below 10 U/mL suggest possible intolerance. Genetic variants (e.g., in DAO or HNMT genes) are sometimes included in consumer DNA tests, but evidence for their predictive value is moderate at best. Diagnosis relies primarily on symptom diaries and elimination diets. Caveat: normal DAO does not rule out histamine intolerance. Overall evidence for blood markers is mixed and not strongly validated.