Diaminoxidase (DAO) is the body's most important enzyme for breaking down food histamine and it is a natural defense mechanism against excess histamine. Hypersensitivity reactions may occur if large amounts of histamine are ingested with the food or the body produces more histamine than can be administered by diaminoxidase. Diaminoxidase is produced in the small intestine, but some medicines, certain foods, and some microbes can suppress its production.
Low levels of diaminoxidase result in the following symptoms and pathological conditions:
- Migraines and headaches
- Vertigo, nausea, vomiting
- Chronic fatigue syndrome
- Hives, skin rashes, eczema, psoriasis
- Nasal congestion, asthma, bronchospasm
- Gastrointestinal disorders, irritable bowel syndrome, diarrhea, flatulence, stomachache, and abdominal cramps
- Dysmenorrhea, premenstrual syndrome, estrogen dominance
- Arrhythmias, hypertension, or hypotension
- Fibromyalgia, muscle aches
- Rheumatoid arthritis
- Neurological conditions such as multiple sclerosis and attention deficit hyperactivity disorder (in childhood and adolescence)
- Disturbances of circadian rhythm
- Neurological disorders related to food intake, body temperature regulation, learning and memory
- Depression, mood disorders, and anxiety
The symptoms that occur when diaminoxidase levels are lower are similar to those of excess histamine since diaminoxidase is the enzyme that breaks down and metabolizes histamine. Patients suffering from urticaria, Crohn's disease, or celiac disease have low diaminoxidase activity in the blood.
Patients who cannot break down histamine develop hypersensitivity reactions to certain foods and on exposure to many substances. These patients' symptoms can be improved by taking appropriate dietary measures and/or taking medications (antihistamines) and dietary supplements.
Because diaminoxidase is produced in the gastrointestinal tract, its low levels are indicative of malfunctioning of the digestive system and intestinal barrier disorder.