What are Diamine Oxidase (DAO) Enzymes?
Diamine Oxidase (DAO) Enzyme
Diamine oxidase, commonly called DAO, is an enzyme the body produces naturally in the lining of the small intestine. Its primary role is to support the breakdown of histamine ingested with food and beverages (exogenous histamine) before it is absorbed into the bloodstream.
DAO is most active in the ileum and jejunum of the small intestine, and it is also found concentrated in the kidney, thymus, and placenta. When dietary histamine in the digestive tract becomes excessive, available DAO helps break down the excess. When DAO activity is reduced or blocked, dietary histamine may accumulate and be absorbed into circulation, where it can interact with histamine receptors throughout the body (Cleveland Clinic).
Shop All DAO Supplements →What is DAO deficiency?
DAO deficiency is not classified as a disease. It describes a functional reduction in DAO enzyme activity that may be associated with individual genetic variation, age, hormonal changes, certain medications, alcohol, and shifts in gut health. In the scientific literature, reduced DAO activity is discussed in relation to what is commonly called histamine sensitivity or histamine intolerance (HIT). The National Institutes of Health (NIH) maintains published, peer-reviewed research on diamine oxidase and its role in histamine metabolism.
What is histamine and which foods are high in it?
Histamine is a naturally occurring compound found throughout the body and in many foods and beverages. When DAO activity is reduced, the body may have a diminished capacity to break down histamine from dietary sources. Foods commonly high in histamine (WebMD) include aged cheeses, fermented foods, cured and processed meats, alcoholic beverages, smoked fish, and certain fruits and vegetables with elevated histamine or histamine-liberating properties.
Histamine receptors are located in the digestive tract, skin, sinuses, cardiovascular system, and neurological pathways. Published research describes a wide range of individual, dose-dependent experiences — meaning effects can vary depending on how many high-histamine foods are consumed alongside other factors such as hormonal fluctuations and stress. These experiences are not specific to any single diagnosable condition; this information is provided for awareness only.
How does supplemental DAO support histamine breakdown?
Supporting the body's natural DAO enzyme activity through dietary supplementation is one approach some individuals explore in consultation with their healthcare providers. A diamine oxidase dietary supplement supplies the same DAO enzyme the body produces naturally to help break down dietary histamine in the gut. When taken before consuming high-histamine foods or beverages, supplemental DAO may support the body's natural histamine-management process in the small intestine before histamine is absorbed into the bloodstream.*
Shop OmneDiem DAO Supplements
OmneDiem produces a family of DAOgest®-based diamine oxidase dietary supplements formulated to support the body's natural DAO enzyme activity. DAOgest® is a naturally derived, clean, porcine-sourced DAO enzyme with an established safety and activity profile in published scientific literature. All OmneDiem® Histamine Digest® products use a designed-release capsule formulated to activate in the small intestine, where dietary histamine is processed.*
Find your fit
Not sure where to start? Match your situation to a product:
| New to DAO and want to try it | Histamine Digest 15,000 HDU → |
| Everyday support before high-histamine meals | Histamine Digest 30,000 HDU → |
| Highest DAO potency, ultra-clean | PureMAX 40,000 HDU → |
| Mast cell & sensitive individuals | Histamine Digest 360 → |
| Before wine, beer & cocktails | Drink HD → |
| Menopause + histamine support | Menopause Complete → |
| Seasonal + dietary histamine & sinus comfort | Histamine Complete → |
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Frequently Asked Questions
What does the DAO enzyme do?
What causes low DAO activity?
Which foods are high in histamine?
When should I take a DAO supplement?
Is DAO deficiency a disease?
Which OmneDiem DAO product is right for me?
Are there any allergens or dietary restrictions?
Related Resources
Diamine Oxidase (DAO) Deficiency
Common Questions About DAO Enzymes
Low-Histamine Diet: Foods & Beverages
*These statements have not been evaluated by the Food and Drug Administration. OmneDiem dietary supplements are not intended to diagnose, treat, cure, or prevent any disease or health condition. This content is for general educational and informational purposes only and does not constitute medical advice. References to third-party sources (including WebMD, NIH, Cleveland Clinic, and others) are provided for informational context only and do not imply endorsement of those sources or their content. Individual results may vary. Consult your healthcare provider before beginning any new supplement regimen, particularly if you are pregnant, nursing, taking prescription medications, or managing a health condition. OmneDiem Histamine Digest products contain a porcine-derived ingredient and are not suitable for individuals with pork allergies or those following vegetarian, vegan, kosher, or halal diets.