Article: DAO enzyme: Function, histamine degradation, and significance in histamine intolerance

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DAO-Enzym im Darm beim Histaminabbau – Illustration zur Histaminintoleranz

Jun 3, 2026Diaminoxidase

DAO enzyme: Function, histamine degradation, and significance in histamine intolerance

DAO (diamine oxidase) is the most important enzyme for the breakdown of histamine in the body. Reduced DAO activity can lead to insufficient histamine breakdown, resulting in the symptoms of histamine intolerance. Learn about the function of the DAO enzyme, where it is produced, and the role it plays in histamine metabolism.

enzymatic breakdown of histamine into imidazole-4-acetaldehyde by diamine oxidase

DAO ENZYME: KEY ENZYME FOR HISTAMINE BREAKDOWN

DAO is an enzymatic molecule that plays a central role in the breakdown of histamine. Histamine is a biogenic amine involved in various physiological processes in the body, but it can lead to unpleasant symptoms if it accumulates excessively. DAO is primarily produced in the small intestine and plays a crucial role in the regulation of histamine metabolism. Histamine is broken down by the DAO enzyme into imidazole-4-acetaldehyde. You can find general information about histamine here.

WHAT IS THE FUNCTION OF THE DAO ENZYME?

The main purpose of diamine oxidase is to deactivate histamine by enzymatically cleaving this molecule. This process allows the body to render histamine inactive, thereby preventing unwanted reactions. DAO acts as a crucial link in the balance of histamine metabolism, as it ensures that the histamine concentration in the body remains at a regulated level.

infographic on intestinal villi, small intestine, and microvilli illustrating nutrient absorption in the gut

WHERE IS DAO PRODUCED IN THE BODY?

DAO is primarily produced in the small intestine cells, particularly in the microvilli of the intestinal lining. It is also found in smaller amounts in other tissues, such as the liver and kidneys. The concentration of DAO in the intestine is especially important, as it is directly linked to the body's ability to process histamine from food.

HISTAMINE INTOLERANCE AND DAO DEFICIENCY

A deficiency of DAO or reduced activity of this enzyme can lead to histamine intolerance. This condition is characterized by symptoms such as headaches, skin rashes, gastrointestinal issues, and respiratory problems. DAO deficiency can be genetic or caused by various factors such as medication use, intestinal issues, or pregnancy.

TREATMENT OPTIONS

The treatment of DAO deficiency aims to alleviate histamine intolerance. This includes adjusting the diet by avoiding histamine-rich foods and, if necessary, adjusting one's lifestyle.

LITERATURE

Maintz, L., & Novak, N. (2007). Histamine and histamine intolerance. The American journal of clinical nutrition, 85(5), 1185–1196.2.

Raithel, M., Baenkler, H. W., Naegel, A., Buchwald, F., & Schultis, H. W. (2007). Significance of salivary histamine levels in food intolerance and buccal inflammation. The American journal of gastroenterology, 102(8), 1711–1717.3.

Schwelberger, H. G. (2009). Diamine Oxidase (DAO) Enzyme and Gene. In: Amine Oxidases: Function and Dysfunction
(pp. 35-52). CRC Press/Taylor & Francis.

Written by Steffi Stahl

DAO explained simply

What is a DAO?

DAO (diamine oxidase) is an enzyme that breaks down histamine in the body – primarily in the gut.

What role does DAO play in histamine intolerance?

If there is too little DAO available or the enzyme is not functioning sufficiently, histamine cannot be broken down as effectively and may potentially accumulate.
Reduced DAO activity is frequently associated with histamine intolerance. Typical symptoms can include headaches, skin reactions, or digestive problems.

Can I support my DAO?

Many affected individuals pay attention to a histamine-conscious diet and a mindful lifestyle. Some additionally use DAO-containing supplements. The quick solution is the intake of the enzyme, but a long-term intestinal rehabilitation is often useful as well. This is because as soon as histamine-producing bacteria occur in increased numbers in the gut, histamine can also accumulate even if enough DAO is present. In that case, however, it can no longer keep up with breaking down the excess.

Is DAO measurable?

DAO activity can be measured in the blood. However, a single value is usually not sufficient to clearly establish histamine intolerance. This makes diagnosing the condition based on values alone often difficult.

Literature

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