Diamine oxidase, activity determination (DAO)

Diamine oxidase (hereinafter referred to as DAO) breaks down histamine. DAO is present in many cells, in the intestines in particular. 

Test for diamine oxidase takes an important part to diagnose the histamine intolerance. Histamine belongs to the biogenic amines group. The related substances are tyramine, phenylethylamine, putrescine, spermine, cadaverine, serotonin, etc. These substances produce the symptoms similar to histamine effect. 

DAO deficiency is one of the causes of histamine intolerance.

Histamine intolerance is developed due to exogenous histamine consumption during diamine oxidase activity decrease. 

DAO activity is reduced by alcohol, variety of medications, chronic inflammatory bowel disease, and  B6 vitamin (coenzyme DAO) deficiency. The disease incidence is about 1%. 

Typical symptoms of DAO concentration decrease are diarrhea, headache (also migraine), viral upper respiratory infections, bronchial asthma, urticaria, dysmenorrhea caused by the large amounts of histamine in food. 

Diamine oxidase inhibiting drugs: acetylcysteine, ambroxol, aminophylline, amitriptyline, clavulanic acid, metamizole, metoclopramide, propafenone, verapamil. 

The symptoms can be triggered by the histamine intolerance along with allergies. In these cases, hyposensitization is less effective.

To verify the diagnosis,  laboratory confirmation is necessary in addition to disease history: test for DAO and vitamin-B6 (if necessary) in serum.