DAO deficiency and allergies

Do you present any skin or respiratory symptoms despite the fact that the skin tests and the IgE are correct? If so, when immunological origins are ruled out, it is necessary to know what the activity of the DAO enzyme is.

Good weather arrives and, with it, the skin and respiratory disorders typical of spring: rhinitis, sneezing, nasal congestion, bronchial asthma, pruritus, redness, hives, etc. You may have gone to the allergist and you have been diagnosed with a food or environmental allergy; or, conversely, that all the tests carried out have been correct, but even so, the symptoms persist.

What do allergy and DAO deficiency have in common? Both in allergy and in DAO deficiency there is an accumulation of histamine levels in the body. However, although both situations have this common denominator, the mechanism of action in each of them is completely different.

On the one hand, a food or environmental allergy is mediated by the immune system and is triggered shortly after having ingested a certain allergen (food) or has come into contact with it (environmental). As we discussed in this article, allergies can cause different signs and symptoms: digestive problems, hives, inflammation of the respiratory tract or other more serious ones, such as an anaphylactic attack. The second time you come into contact with the allergen, IgE antibodies will detect it and tell the immune system to release histamine and other chemicals into the blood. Once the histamine is released, it travels through the bloodstream until it reaches the receptors located in the different systems of the organism and, consequently, the appearance of the symptoms is unleashed. In this way, the treatment to follow will be to avoid the allergen, as well as those other foods which may have been in contact with it due to cross-contamination. In case of environmental or idiopathic allergies, antihistamines are usually prescribed. However, it should be noted that some people who have an allergy problem also have a DAO deficiency. In these cases, one aspect to take into account will be to find out if the person makes chronic use of antihistamines, since there are some of them described as DAO enzyme blockers.

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On the other hand, when there is a DAO deficiency, there is a malfunction of the histamine degradation systems; either due to a primary (genetic) or secondary origin (inflammatory bowel diseases, pharmacological blockade, consumption of alcoholic beverages…). Consequently, food histamine, which does not fulfill any function in the body, should be eliminated, but an excessive accumulation of it is generated, activating the different histamine receptors in the body. Unlike allergies, the appearance of symptoms is not linked to the consumption of a specific product, but to exceeding the threshold for histamine accumulation from food. This fact means that the symptoms do not appear immediately, but rather that the levels accumulate over time and, when these exceed the body’s metabolizing capacity, the symptoms appear. It is a dose-dependent response, unlike an allergy. The therapeutic strategy should be aimed at a personalized low-histamine diet and other amines that favor their accumulation and, gradually, expand the variety, quantity and frequency of consumption of these foods. The purpose will be to find which level the body can tolerate correctly without the symptoms appearing again. In addition, in most cases, DAO enzyme supplementation is used as an adjuvant in the treatment.

For this reason, if you suffer from any respiratory or skin symptoms not related to any allergy and possible immunological origins have been ruled out, the activity of the DAO enzyme should be checked and, in the best of cases, a genetic test should also be carried out to evaluate the possibility of a genetic DAO deficiency. Even if you have a diagnosed environmental allergy, but you have not just improved with the medical treatment, it could be that you also had a DAO deficiency and this was the cause of the continuity of the symptoms. In this way, if the result comes out with a reduced DAO activity or the positive genetic test, it will be necessary to start an individualized treatment for each case and always in the hands of a specialized dietitian-nutritionist.


Comas-Basté O, Sánchez-Pérez S, Veciana-Nogués MT, Latorre-Moratalla M, Vidal-Carou MDC. Histamine Intolerance: The Current State of the Art. Biomolecules. 2020 Aug 14;10(8):1181. doi: 10.3390/biom10081181. PMID: 32824107; PMCID: PMC7463562.

Mayo-Yáñez, M., Díaz-Díaz, A., Calvo-Henríquez, C., Lechien, J. R., Vaira, L. A., & Figueroa, A. (2023). Diamine Oxidase Activity Deficit and Idiopathic Rhinitis: A New Subgroup of Non-Allergic Rhinitis?. Life (Basel, Switzerland)13(1), 240. https://doi.org/10.3390/life13010240

Schnedl, W. J., & Enko, D. (2021). Histamine Intolerance Originates in the Gut. Nutrients13(4), 1262. https://doi.org/10.3390/nu13041262

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