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What to Know About Diamine Oxidase (DAO) for Histamine Intolerance

Medically Reviewed by Dan Brennan, MD on June 09, 2021

Diamine oxidase (DAO) is an important digestive enzyme in your body. Some people take diamine oxidase supplements to help with histamine intolerance, which can cause migraines and headaches, gut issues, and skin conditions.

Here's what you need to know about DAO and whether or not supplements can help with histamine intolerance.

What Is Diamine Oxidase (DAO)?

Diamine oxidase (DAO) is an enzyme that your body makes to break down histamine from foods. If your body doesn't produce enough DAO, you may have diamine oxidase deficiency. ‌

Without enough of this enzyme, you can experience histamine intolerance, also called food histaminosis or enteral histaminosis. This can make you sick when you eat foods that contain histamine.

Some high-histamine foods include:‌

  • Wine
  • Beer 
  • Avocado
  • Nuts
  • Milk
  • Soybeans
  • Mushrooms
  • Chocolate
  • Shellfish
  • Eggs
  • Oily fish
  • Strawberries
  • Pineapple

A histamine intolerance is different from allergies, as it’s not linked to one specific food and doesn’t cause immune cell reactions. With this intolerance, it can sometimes be hard to pinpoint what food gives you symptoms. ‌

Your body also makes histamine. If you have too much histamine in your gut and it's released from your cells, you can end up with too much histamine collecting in your blood. This causes symptoms including:

  • Migraines
  • Bloating 
  • Feeling sick
  • Gas
  • Stomach pain
  • Throwing up
  • Constipation
  • Fullness
  • Muscle aches
  • Pain
  • Stuffy nose
  • Asthma
  • Hives
  • Dizziness
  • Psoriasis 

Benefits of Diamine Oxidase Supplements

Diamine oxidase (DAO) supplements are over-the-counter products that restore the diamine oxidase enzyme in your body. They help break down histamine-rich foods and may reduce symptoms of histamine intolerance. 

Research shows that these supplements might offer relief from headaches, digestive issues, and skin reactions. While these studies show positive results, more research is needed to understand how DAO supplements work and if they can help reduce symptoms of histamine intolerance in the majority of people.

Migraines and headaches. In one study, people with irregular migraines supplemented with DAO for over one month. The supplement significantly lowered the length of migraine attacks by almost 90 minutes. 

Digestive symptoms. People with histamine intolerance who took DAO supplements showed improvement in at least one digestive symptom. This study was small, so more research is needed to understand these effects. 

In another study, patients with histamine intolerance who took DAO supplements for four weeks experienced fewer and less intense digestive symptoms. The researchers suggested that the lining of the gut might have healed while taking the supplement.‌

Skin conditions. DAO supplements may also help relieve hive symptoms. In one controlled study, people with low levels of DAO and chronic hives who took DAO were able to lower their antihistamine medication dose.

Risks of Diamine Oxidase Supplements

One of the problems with histamine intolerance is that there aren’t any tests that can diagnose it. So, while DAO supplements may help some symptoms, they may not be safe to take if you actually don't have the condition.‌

Also, there aren’t any standards for making supplements, so you might find products with different recommendations and doses and unclear labels. These could be unsafe to consume. 

Some supplements are made with animal kidney extracts, specifically kidneys from pork. This may be important if you follow religious or other dietary restrictions on animal products. ‌

Generally, though, there isn’t enough quality research yet to know exactly how DAO supplements work and the safety of them. Larger studies with more people being treated for a longer period of time are necessary.

Alternatives to Diamine Oxidase Supplements

There are lots of factors to histamine intolerance, but one way of managing your symptoms without supplements is to follow a low-histamine diet. This can stop too much histamine from gathering in your body, which can improve symptoms. 

Clinical studies show that a low-histamine diet can improve histamine intolerance. Results show that more than 50% of people have reported reduced symptoms. However, some studies found that a low-histamine diet didn’t change the enzyme activity in the body.  

There are no specific recommendations on a low-histamine diet because histamines are in lots of different foods (see the list above). You can try to eliminate foods that cause you the most symptoms.

Considerations for Diamine Oxidase and Histamine Intolerance

DAO is an important enzyme that helps you break down food. A lack of DAO can cause symptoms that act like allergies but aren’t.   ‌

Instead of taking DAO supplements, the best approach may be to avoid high-histamine foods that bother you. If you’re having symptoms and considering taking DAO supplements, talk to your doctor first.

WebMD Medical Reference

Sources

SOURCES:

American Academy of Allergy Asthma & Immunology: “Diamine oxidase use in children.”

The American Journal of Clinical Nutrition: “Histamine and histamine intolerance.”

Biomolecules: “Histamine Intolerance: The Current State of the Art.”

Clinical Nutrition: “Diamine oxidase (DAO) supplement reduces headache in episodic migraine patients with DAO deficiency: A randomized double-blind trial.”

Food Science and Biotechnology: “Diamine oxidase supplementation improves symptoms in patients with histamine intolerance.”

Harvard Health Publishing: “Food allergy, intolerance, or sensitivity: What’s the difference, and why does it matter?”

International Archives of Allergy and Immunology: “Diamine Oxidase Supplementation in Chronic Spontaneous Urticaria: A Randomized, Double-Blind Placebo-Controlled Study.”

International Journal of Immunopathology and Pharmacology: “Serum diamine oxidase activity in patients with histamine intolerance.”

International Society of DAO Deficiency: “What is DAO deficiency?”

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