Why test for Diamine Oxidase?
Histamine intolerance is defined by the balance of histamine and the histamine degrading enzyme diamine oxidase (DAO), which is mainly produced in the small intestine. Because of histamine intolerance (HIT) maybe drugs, which are inhibitors of the diamine oxidase. Alcohol and its degradation product acetaldehyde are inhibitors too. Additionally yet unknown effects on the activation of isoforms may have the influence of the histamine-degrading capacity. Typical symptoms of histamine intolerance are headache, diarrhea, migraine, engorged or dripping nose and especially in connection with food incorporation asthma and arrhythmia, hypotension, urticaria, dysmenorrhea. Those with anaphylactic reactions also have lower histamine activity.The diagnosis of histamine intolerance is achieved by the determination of diamine oxidase activity in serum. Following a histamine – free diet normally results in significant reduction or even disappearance of the symptoms within a few weeks.
The diagnosis of histamine intolerance based on the activity of diamine oxidase hence is only admissible when the activity is low. Nonetheless, when normal DAO activity and simultaneously increase the histamine – levels are found, symptoms of histamine intolerance maybe present. Especially after extreme histamine exposure like an anaphylactic shock increased activity of diamine oxidase and elevated histamine levels were measured. Therefore the interpretation of diamine oxidase always has to be done in context. If DAO is low, this constitutes diamine oxidase deficiency. However, if DAO is normal with a high histamine, this also indicates an insuffciency which will trigger symptoms. Patients suffering from diseases like Urticaria, Chrons, Celiac Disease are reported to show low DAO activity in serum or plasma. Furthermore, DAO is described as marker for the status of the gut mucosa. Patients with chronic gut failure often show have reduced DAO values.