Histamine is a simple chemical substance with a molecular weight of 111 Da. It is the most important mediator of allergic diseases like rhinitis allergica (hay fever) and asthma bronchiale. Furthermore histamine is the major cause for urticaria and is an important
mediator of drug allergy.
In case of histamine-intolerance various physiological reactions as dilatation of blood vessels, contraction of the uterus are seen. Furthermore irritating effects like headache, engorged respiration, dripping nose, airway obstruction, tachycardia, extrasystoles and
gastrointestinal-ailments, which can cause soft stool up to diarrhoea and hypotension. Often tumescence of eyelids and sometimes urticarial exanthema were described as well.
Histamine is produced within the body and stored in mast cells for immediate release. Additionally histamine is either inhaled (histamine-provocation) or ingested with food containing high levels of histamine or other biogenic amines.
The main enzyme for metabolism of ingested histamine is diamine oxidase (DAO). The copper-containing enzyme with a molecular mass of 90 kDa is produced predominantly in the enterocytes. Mainly the enzyme is found in the small intestine, the liver, the kidney and in white blood cells. During pregnancy huge amounts of the enzyme are produced in the placenta, resulting in up to 500 to 1000 fold higher concentrations of the enzyme in the circulation. Because of these high levels of DAO no allergic problems normally are seen in women in the time of 3rd to 9th month of pregnancy.
DAO is produced continuously and secreted into the intestine. Therefore most of the histamine ingested with food normally is metabolised immediately within the bowel. Remaining histamine is removed by DAO present in the mucous membrane. It is degraded to imidazol acetaldehyde and further oxidised to imidazole acetic acid. Postulated cofactors of DAO are 6-hydroxy-dopa and vitamin B6. Diamine oxidase is a rather sensitive enzyme, it is inhibited by other biogenic amines, ethanol, it´s degradation product acetic aldehyde and by many different drugs.
Histamine intolerance is defined by an imbalance of histamine and the histamine degrading enzyme diamine oxidase, which is mainly produced in the small intestine. The present clinical experiences show that histamine intolerance isn`t congenital, but rather an acquired disease. A cause of histamine - intolerance (HIT) may be drugs, which are inhibitors of the diamine oxidase. Alcohol and its degradation product acetaldehyde are inhibitors too.
IMM12 - DAO Histamine Test
DAO Histamine Test
Test Type:Blood Serum