About DAO
DAO is a copper-dependent enzyme (typically porcine kidney-derived) that degrades dietary histamine in the gut lumen. Small trials in histamine intolerance report symptom improvement, but the evidence base is small and heterogeneous. Dosing is expressed in histamine-degrading units (HDU), which vary by product.
What DAO supports
- May ease histamine-intolerance symptoms - small trials only, not confirmed
Clinical evidence
Limited clinical evidence. Only small trials in histamine intolerance; no large RCTs.
NIH Fact Sheet