What is this test?
DAO is an enzyme involved in breaking down histamine, especially in the gut. Measuring its activity may provide supporting information for selected symptoms.
Why might it be ordered?
- For recurrent symptoms after foods rich in histamine, after exclusion of better established causes.
- As part of a specialist assessment, not as a stand-alone screening.
What sample is needed?
A healthcare professional collects a venous blood sample. Depending on the method, the laboratory uses serum or plasma.
How should you prepare?
Food, drugs and supplements can affect the result. Follow the specific laboratory protocol and do not stop treatment without a doctor's instruction. Tell the laboratory about all medicines, hormone treatments, vitamins and supplements you take. Do not stop or change treatment unless your clinician tells you to. Follow any instructions about fasting and the time of collection.
How should you understand the result?
Low DAO activity may be a supporting finding, but it does not prove that histamine is causing the symptoms. Your result is interpreted using the reference interval on the laboratory report and in the context of your symptoms, medical history and other test findings.
Sources and editorial status
This patient-facing text is an editorial draft. It should be approved by a laboratory physician before official publication.