Supplement analysis backed by scientific evidence · PT

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Limited evidenceGut health

Diamine Oxidase (DAO)

The enzyme that breaks down histamine in the gut, sold for histamine intolerance. Two small randomized trials in related conditions are cautiously positive, while histamine intolerance itself still has no completed trial.

Evidence last reviewed: August 2026

What the science says

  • Migraine in people with low DAO Limited evidence

    A randomized double-blind trial in episodic migraine patients selected for DAO deficiency found shorter headache duration with supplementation. It was a small trial in a preselected group and has not been replicated.

  • Chronic spontaneous urticaria Limited evidence

    A randomized, double-blind, placebo-controlled study of DAO supplementation in chronic spontaneous urticaria reported symptom improvement. The sample was very small and the effect modest.

  • Histamine intolerance itself Limited evidence

    Despite being the main marketing claim, no completed randomized trial has tested DAO for histamine intolerance. A trial protocol has been published, but results are not yet available.

Dosage & safety

Studied doseTrials used a porcine-kidney DAO preparation taken before meals up to three times daily for about a month. Commercial products state activity in histamine-degrading units, and these vary widely between brands.
SafetyWell tolerated in the short trials. It is derived from porcine kidney, so unsuitable for pork-free diets, and it acts only in the gut, doing nothing about histamine already absorbed. Symptoms attributed to histamine intolerance overlap with mast cell disorders, allergy and IBS, which need proper assessment.

Scientific references

Where to buy

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