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DAO supplements may help break external histamine sources thereby relieving skin rashes, digestive issues, headaches that might occur due to DAO deficiency or histamine overproduction. However, the supplements can never be a cure that readily replaces DAO since they can not break down internally-produced histamine.

Diamine Oxidase (DAO) is an enzyme produced by the body to scale down the overproduction of histamine, but it is also available as a supplement. DAO supplements are usually taken to relieve headaches and migraines, skin rashes, or digestive issues resulting from excess histamine production through external sources. However, DAO deficiency is a serious medical condition that cannot be cured by supplementing with DAO since the latter cannot break down internally-generated histamine. Medical studies on DAO supplements are only a few and are at the preliminary stages, leaving the dosage recommendation for the supplements uncertain. Here is everything you need to know about DAO and its supplements.

Understanding DAO

Before exploring the nitty-gritty about DAO, you need to understand what it is. Simply put, it is an enzyme produced by the kidney, digestive tract’s intestinal linings, and the thymus. It is digestive in nature and secreted to help the body break down and eliminate excess histamine. Histamine is a natural compound in the body that helps with immune, digestive, and nervous functions but whose excess amounts steer allergies. DAO deficiency makes the body less efficient at breaking down and eliminating histamine, resulting in various allergic reactions such as digestive issues, skin rashes, itchy skin, running nose and sneezing, and asthma. DAO deficiency and histamine intolerance present themselves in the same way and manifest the same symptoms, making it difficult to diagnose DAO deficiency accurately.

Diet may introduce histamine to the body

Histamine occurs naturally, but our foods can also introduce it to the body. For instance, if you eat aged foods such as wine, cheese, pickles, and other fermented products, you are likely introducing histamine to your body. Besides, cured foods such as cured or smoked meat also have histamine, and eating them supplies more of this compound to the body.

Histamine intolerance may be caused by DAO deficiency

DAO deficiency describes the condition when the kidney, thymus, and intestinal tract walls do not produce enough DAO enzyme. Contrarily, histamine intolerance refers to the medical condition that develops when the histamine levels shoot up in the cells, resulting in a series of uncomfortable side effects. Although DAO deficiency may cause histamine intolerance, there are many other causes of this condition, including eating histamine-containing foods, alcohol consumption, genetic factors, and overgrowth of intestinal bacteria on the stomach. Histamine intolerance manifests like many other medical conditions and has mild to severe effects such as itchy skin, sneezing, asthma, nausea, and digestive issues, irregular heartbeat, low blood pressure, etc. The mentioned symptoms may be related to other conditions, making it unwise to do self-diagnosis for histamine intolerance and start taking DAO supplements. As with other supplements, you need to consult a qualified medical advisor before introducing supplements to your system.

DAO supplements

DAO supplements are available in physical stores and online, and many people take them to manage allergic reactions. Although research on the effectiveness of DAO supplements for the conditions for which they are taken is limited, those who have used them say that they may help relieve some symptoms. For instance;

  • They may relieve digestive issues

Some people have found relief for their digestive issues when they supplemented with DAO. For instance, one study lasted two weeks and gave its participants 4.2 g of DAO throughout the study. In the end, more than 90% of the participants reported that the supplement helped relieve at least one symptom of digestive problems, including abdominal cramping, gas, bloating, and diarrhea.

  • They may ease skin rashes

Skin rash affects many people, most of whom use antihistamine medication to ease the rashes. Some studies claim that supplementing with DAO could work as effectively as antihistamine drugs and in relieving the rashes. For instance, in a month-long study, 20 participants who used DAO supplements twice a day for their rashes recorded a significant reduction in the frequency and intensity of skin rashes.

  • They may help reduce headaches and migraine attacks

Headaches affect many people, especially now that stressors are on the rise. Recent studies suggest that supplementing with DAO could help reduce the frequency of migraine attacks, especially when it is DAO deficiency-induced. For instance, a 30-day long observed that participants who took daily doses of DAO received a 23% reduction in the frequency and intensity of migraine attacks.

The observations above are quite promising. However, there is limited research to support these claims, considering that studies about DAO supplementation are only at the preliminary stages. As if that’s not enough, not everyone in the study cohorts experienced positive observations, meaning we are still far from it. As such, supplementing with DAO basically because you have DAO-deficiency-like symptoms is an unwise move.

Nutritionally enhancing DAO function

DAO deficiency may result in several health challenges, including histamine intolerance. As such, working around your diet is the best way to scale down histamine levels without necessarily taking DAO supplements. There are two nutritional therapies for enhancing DAO function, including;

  • Eat low-histamine foods

Eating low-histamine foods helps keep the histamine levels just where the body wants them. Thankfully, there are many food options with low histamine count, including grains, fresh meat, nuts, seeds, fresh fruits, and eggs. Of course, they have some histamine, but the levels are lower than many other foods.

  • Avoid histamine-rich foods

Histamine-rich foods supply the body with more histamine than it needs. Although dietary histamine is only external, it triggers negative side effects like internally-produced histamine. Cured or smoked meat, aged foods, and drinks, including wine and cheese, certain vegetables, including avocado and spinach, and certain preservatives, colorings, and flavorings are histamine-rich and will cause histamine intolerance. Consequently, limiting or avoiding them helps enhance DAO function.


DAO is an enzyme naturally produced by the body to break down and eliminate histamine. It is also available in supplements marketed to manage histamine intolerance and DAO deficiency. Although such supplements may help reduce skin rashes, headaches, and digestive issues related to histamine intolerance, they cannot cure DAO deficiency. Furthermore, more studies are needed to establish whether DAO supplements really work to treat DAO-deficiency-related symptoms.

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Ksenia Sobchak, BA (Hons) Fashion Communication: Fashion Journalism, Central Saint Martins Ksenia Sobchak enjoys blogging on fashion, style, lifestyle, love and CBD areas. Prior to becoming a blogger, Ksenia worked for a renowned fashion brand. Ksenia is a contributing author to leading fashion, lifestyle and CBD magazines and blogs. You can bump into Ksenia at her favourite cafe in South Kensington where she has written most blogs. Ksenia is a staunch advocate of CBD and its benefits to people. Ksenia is also on the panel of CBD reviewers at CBD Life Mag and Chill Hempire. Her favourite form of CBD are CBD gummies and CBD tinctures. Ksenia is a regular contributor at leading fashion, lifestyle as well as CBD magazines and blogs.

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