Taken with meals

Seeking Health DAO Enzyme Capsules

Diamine oxidase, the enzyme that breaks down dietary histamine, for people whose reactions follow aged cheese, wine and leftovers.

Format: Capsule
Type: Digestive enzyme
Cost: $1.03 a day
Customer rating: 4.3 out of 5 from 2,236 ratings from Amazon

Buy it at iHerb

What customers consistently report

Eating previously off-limits foods without the flush, headache or gut upset
Working within the meal it is taken with
No loose stools even at higher doses, which one reviewer singles out

Those are the themes that recur across the reviews. High review confidence — 4.3 from 2,236 Amazon ratings.

Why it might work

Histamine in aged, fermented and leftover foods is normally broken down in the gut lining by diamine oxidase before it is absorbed; people with low DAO activity absorb more and react to it. A capsule of the enzyme taken just before eating adds DAO to the gut contents so that dietary histamine is degraded there. It does not cross into the blood and does nothing for histamine the body makes itself.

What the research supports

Ingredient-level evidence, preliminary. A 2019 open-label pilot study gave 28 people with histamine intolerance diamine oxidase capsules before meals for four weeks: symptom scores across 22 symptoms improved significantly and rose again after stopping. Without a placebo group, that cannot separate the enzyme from expectation, and a 2024 protocol for a randomized, double-blind trial of DAO plus a low-histamine diet has been published without results. No trial of this brand was found.

What the label discloses

The capsule supplies a patented DAO2 diamine oxidase derived from porcine kidney; the activity units are stated on the pack rather than the listing. Seeking Health states the product is made without the major allergens except that the enzyme source is pork. The label carries clear statements that it is not for immune allergies or celiac disease. No third-party testing certificate is published.

Who this tends to suit

We match this product to people reporting symptoms that follow particular foods, general abdominal discomfort, bloating and loose stools. It fits someone whose priority is handling meals or day-to-day comfort. Whether it is the best fit for you depends on the rest of your answers — what you have already tried, what format you will take, and anything that has to be ruled out.

Where it may not fit

The label supports gluten-free, dairy-free and no added sweeteners. We flag this product for anyone pregnant or breastfeeding, and the quiz removes it rather than recommending it in those cases. That is a caution about who should be deciding, not a claim about the product. A capsule only works if you will take it as often as the label directs.

Side effects and what to be aware of

It is the most expensive enzyme in the catalog at a dollar a capsule, and the evidence is an open-label pilot with no placebo group; a controlled trial is registered but not reported. The enzyme is extracted from pig kidney, so it is not vegetarian or halal. It does nothing for immune food allergies or for celiac disease, as the label itself states. Headaches and stomach aches are reported by a minority.

Before you take this. Speak to a doctor or pharmacist first if you are pregnant or breastfeeding. Nothing on this page is medical advice, and no supplement diagnoses, treats, cures or prevents disease.

Buy it at iHerb

Is this the right one for you?

The quiz works out which of the products we have researched fits your symptoms, your routine and what you have already tried — and tells you plainly if none of them do.

Take the quiz →

Free. Private. Nothing to sign up for.