RetzlerRx® DAO Enzyme provides 30,000 Histamine Degrading Units (HDU) of diamine oxidase per capsule. DAO is concentrated in the intestinal mucosa, where it helps metabolize histamine from food before much of that histamine is absorbed. Taken shortly before a meal, supplemental DAO provides targeted digestive support when dietary histamine is a concern.*
RetzlerRx® DAO Enzyme 30,000 HDU is a concentrated DAO formula designed to support the metabolism of food-derived histamine within the gastrointestinal tract.* Each capsule contains 4.2 mg of porcine kidney extract (DAOgest®), providing 30,000 HDU of diamine oxidase.
DAO has a specific physiological role. It is highly expressed in the intestinal mucosa, particularly in the small intestine, where it helps metabolize histamine present in food before that histamine moves into the circulation. Supplemental DAO is therefore generally used shortly before eating rather than as a general-purpose systemic histamine supplement.*
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Histamine is a normal signaling molecule involved in immune activity, digestion, nervous-system signaling and blood-vessel regulation. It is also present in food. Aged cheeses, cured meats, fermented foods, wine, beer and certain fish can contain substantially more histamine than many freshly prepared foods.
Diamine oxidase, usually shortened to DAO, is one of the body's principal enzymes for handling this dietary histamine. DAO is concentrated in the intestinal lining, where it helps break down histamine before much of it is absorbed.
RetzlerRx® DAO Enzyme provides 30,000 HDU of DAO in one capsule and is designed to be taken shortly before a meal. Its role is intentionally narrow: supporting the metabolism of histamine arriving through food.* DAO does not block histamine receptors throughout the body, and it should not be confused with an antihistamine medication or treatment for an IgE-mediated food allergy.
For people who notice a consistent relationship between certain meals and symptoms, supplemental DAO can be one practical tool while diet, gastrointestinal health and the broader clinical pattern are considered.
- Supporting the breakdown of dietary histamine before absorption.*
- Supporting digestive comfort around histamine-containing foods.*
- Providing additional DAO enzyme activity around meals.*
- Adults who notice a reproducible sensitivity to histamine-rich foods.*
- Those looking for a higher-activity 30,000 HDU DAO capsule.*
What Is Diamine Oxidase?
Diamine oxidase (DAO) is an enzyme involved in the metabolism of extracellular histamine. It is highly expressed in the intestinal mucosa and is particularly active in the small intestine.
Within the digestive tract, DAO contributes to an enzymatic barrier between histamine contained in food and the systemic circulation. By metabolizing histamine while it is still in the intestinal lumen, DAO helps limit the amount of dietary histamine available for absorption.*
DAO is also found in other tissues, including the colon, kidneys, thymus and placenta, but its intestinal activity is especially relevant when discussing food-derived histamine.
Histamine Is Not Inherently a Problem
Histamine is a normal biogenic amine made from the amino acid histidine. The body uses it as an immune mediator, neurotransmitter and local signaling molecule. Through its different receptors, histamine participates in vascular regulation, gastric physiology, smooth-muscle activity and sensory signaling.
The goal of DAO supplementation is therefore not to eliminate histamine from the body. Its intended role is much more specific: supporting the metabolism of histamine encountered through food within the gastrointestinal tract.*
Where Dietary Histamine Comes From
Histamine can accumulate in food when microorganisms convert histidine into histamine. Fermentation, aging, curing, processing and storage can all influence how much histamine a food contains.
Foods commonly associated with higher dietary histamine exposure include:
- Aged and matured cheeses
- Cured and processed meats
- Fermented foods
- Wine and beer
- Certain fish and seafood
- Foods stored as leftovers for extended periods
This does not mean these foods are unhealthy or that everyone should avoid them. Histamine content varies from one food and preparation method to another, and individual tolerance varies considerably.
30,000 HDU Per Capsule
DAO supplements are generally described according to Histamine Degrading Units, or HDU. HDU describes enzyme activity rather than simply reporting the physical weight of the ingredient.
Serving Size: 1 Capsule
Servings Per Container: 60
Porcine Kidney Extract (DAOgest®): 4.2 mg
Providing 30,000 HDU Diamine Oxidase (DAO)
Daily Value not established.
The 30,000 HDU activity level makes this a concentrated option for individuals who want targeted DAO support around meals.*
Why Timing Matters
Supplemental DAO is intended to be present in the gastrointestinal tract when dietary histamine arrives. For that reason, timing the capsule close to a meal is consistent with the way the enzyme is intended to function.
Suggested Use: Take 1 capsule approximately 15 minutes before a meal, or as recommended by your health care professional.
DAO Is Not the Same as an Antihistamine
Antihistamine medications generally work by blocking histamine receptors. Supplemental DAO works differently. It is an enzyme intended to help metabolize histamine within the digestive tract.*
This distinction is important because many symptoms commonly attributed to “histamine” can have other causes. Headache, flushing, nasal symptoms, itching and gastrointestinal discomfort are not specific to impaired dietary histamine metabolism.
A response to DAO may be useful information, but it should not automatically become a diagnosis.
Histamine Intolerance Is More Complicated Than a Food List
The term histamine intolerance is generally used when symptoms appear to result from an imbalance between dietary histamine exposure and the body's ability to metabolize it. Reduced intestinal DAO activity is one proposed contributor.
There is no single symptom or laboratory test that establishes histamine intolerance in every patient. Dietary exposure, intestinal health, medications, alcohol intake, genetics and other medical conditions may all influence how someone responds.
This is one reason we prefer targeted support over indefinite food restriction. When histamine-rich foods appear to cause a reproducible problem, temporary dietary modification, careful reintroduction and appropriate clinical evaluation can be more informative than progressively eliminating foods without understanding the pattern.
DAO and Food Allergy Are Different
DAO supplementation should not be used to prevent or treat an IgE-mediated food allergy. Food allergy involves a different immune mechanism and can produce severe or life-threatening reactions.
Anyone experiencing throat tightness, facial or tongue swelling, wheezing, difficulty breathing, faintness or a history of anaphylaxis requires appropriate medical evaluation. DAO should never be used as protection before deliberately consuming a known allergenic food.
DAO and Mast Cell Disorders Are Also Different
Mast cells can release histamine produced within the body. Oral DAO, by contrast, is primarily intended to support metabolism of histamine encountered within the gastrointestinal tract.*
Symptoms can overlap, but a mast-cell disorder and impaired handling of dietary histamine are not interchangeable diagnoses. Persistent or unexplained symptoms deserve appropriate medical evaluation rather than assuming that increasing DAO intake will address the underlying problem.
DAO Within a Broader Gut-Health Strategy
DAO can be useful when the immediate issue is dietary histamine, but intestinal physiology extends well beyond a single enzyme. The condition of the intestinal mucosa, microbiome, barrier function, gastrointestinal motility, diet and medication exposure can all influence how someone responds to food.
For a broader clinical discussion, read the HormoneSynergy® Gut Health and the Microbiome: How the Gut Influences Metabolism, Immunity, and Longevity.
For our broader approach to nutritional supplementation, read Supplements in Longevity Medicine: What Helps, What Is Hype, and Where We Stop.
DAO Enzyme 30,000 HDU or Hist Arrest?
HormoneSynergy® carries two RetzlerRx® DAO options for people seeking targeted support around dietary histamine.*
RetzlerRx® DAO Enzyme provides 30,000 HDU per capsule from porcine kidney extract (DAOgest®). It is the higher-activity option and is intended to be taken approximately 15 minutes before a meal.*
RetzlerRx® Hist Arrest provides 20,000 HDU per tablet and offers another option for targeted DAO support around meals.*
You can also browse the HormoneSynergy® Gut Health, Histamine & Probiotics Collection for additional digestive and gut-barrier support options.
Who May Consider DAO Enzyme 30,000 HDU?
DAO supplementation may be considered by adults who notice a reasonably consistent relationship between histamine-rich foods and digestive or other food-associated reactions, particularly when the goal is to support intestinal metabolism of dietary histamine.*
Because this product uses porcine kidney extract, it is not suitable for vegetarian or vegan diets and may not be appropriate for individuals who avoid pork-derived ingredients.
Suggested Use
Take 1 capsule approximately 15 minutes before a meal, or as recommended by your health care professional.
DAO is intended for use in relation to dietary histamine exposure rather than as a substitute for identifying persistent or medically significant food reactions.
Frequently Asked Questions
What does RetzlerRx® DAO Enzyme do?
It provides supplemental diamine oxidase to support the breakdown of histamine from food within the gastrointestinal tract before much of that histamine is absorbed.*
How much DAO is in each capsule?
Each capsule provides 30,000 Histamine Degrading Units (HDU) from 4.2 mg of porcine kidney extract (DAOgest®).
How many capsules are in each bottle?
Each bottle contains 60 capsules.
When should I take DAO Enzyme?
The suggested use is one capsule approximately 15 minutes before a meal, or as recommended by your health care professional.
Does DAO lower histamine throughout the entire body?
Oral DAO is primarily intended to support metabolism of dietary histamine within the gastrointestinal tract.* It should not be viewed as a systemic antihistamine.
Is DAO the same as an antihistamine medication?
No. Antihistamine medications generally block histamine receptors. DAO is an enzyme that helps metabolize histamine within the digestive tract.
Can DAO treat a food allergy?
No. DAO supplementation should not be used to treat or prevent an IgE-mediated food allergy or anaphylaxis.
Can DAO be used for environmental allergies?
This product is formulated around the metabolism of food-derived histamine within the gastrointestinal tract.* It should not be presented as a treatment for pollen, animal dander or other environmental allergies.
What is the difference between DAO Enzyme 30,000 HDU and Hist Arrest?
DAO Enzyme provides 30,000 HDU per capsule from porcine kidney extract (DAOgest®). RetzlerRx® Hist Arrest provides 20,000 HDU per tablet. Both are intended to support the metabolism of dietary histamine within the digestive tract.*
Is DAO Enzyme 30,000 HDU vegetarian?
No. The DAO ingredient is derived from porcine kidney extract.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.