Diamine oxidase

Diamine oxidase (DAO), also known as histaminase, is an enzyme that breaks down histamine. The highest concentrations of DAO are found in the digestive tract and the placenta. Two studies have investigated serum levels of DAO as a potential diagnostic test for histamine intolerance (HIT), but this is not a widely accepted diagnostic test.

Supplementation
DAO food supplements are taken for histamine intolerance in patients with low DAO, for example the supplement DAOsin.

DAO food supplements form are sometimes taken by individuals with mast cell activation disorder.

In rats, Magnesium is an important cofactor in the production of DAO and magnesium deficiency may result in decreased DAO activity and excess histamine levels.

Copper, Vitamin B6 and Vitamin C are other important DAO cofactors.

Heparin increases the activity of DAO in the blood.