Diamine oxidase (DAO) is a digestive enzyme produced in your kidneys, thymus, and the intestinal lining of your digestive tract.

Its primary function is to break down excess histamine in your body (1).

Histamine is a naturally occurring compound that helps regulate specific functions of your digestive, nervous, and immune systems.

If you’ve ever experienced an allergic reaction, you’re probably familiar with common symptoms associated with elevated histamine levels, such as nasal congestion, itchy skin, headaches, and sneezing.

You may also ingest histamine through your diet. It naturally occurs in certain foods — especially those that are aged, cured, or fermented like cheese, wine, pickles, and smoked meats (1).

DAO keeps histamine levels in a healthy range to avoid uncomfortable histamine-induced symptoms.

Summary

Diamine oxidase (DAO) is an enzyme that helps break down excess histamine in your body, thus easing uncomfortable symptoms, such as nasal congestion, itchy skin, headaches, and sneezing.