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.

DAO is also available as a food supplement under the brand names DAOSin, DAO Histaminase, Histame, HistamAid88, and Dao Histamine Digester Supplement, and others.

Theory
DAO levels in the body cannot be changed, but DAO supplements taken with a meal can reduce the levels of histamine absorbed from that meal, reducing the severity of any histamine reactions.

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.

Cost and availability
DAO supplements are available without a prescription. Some DAO supplements contain extra active ingredients such as quercetin, rutin, vitamin C or other vitamins, calcium or other minerals, plus inactive ingredients including stabilizers, or preservatives.

Learn more

 * DAO: What you need to know - Histamine Sensitivity
 * The Food List - Histamine Intolerance

Low Histamine Foods (downloads)

 * ISHI Histamine Elimination Diet
 * Histamine-reduced diet - DAO Deficiency
 * Low Histamine Food List