The study of the activity of the Diamine Oxidase (DAO) enzyme is a diagnostic test that measures the ability of this enzyme to break down histamine in the body. Histamine is a substance that plays an important role in allergic responses and is also found in many foods. Low activity of the DAO enzyme can lead to an excess of histamine, causing symptoms such as migraines, digestive problems, and allergic reactions.

Can be modified by: genetic factors, medications, diet, and gastrointestinal diseases.