Evidence-based·Last reviewed May 30, 2026·How we grade evidence

Diamine Oxidase

Enzyme

Useful mainly for people with confirmed histamine intolerance reacting to histamine-rich foods.

Quick decision guide

May help most

People with confirmed histamine intolerance reacting to histamine-rich foods

Common dosing range

One capsule (commonly 4,200–30,000 HDU) before histamine-rich meals

When to expect effects

Within the meal; effect is short-lived

Watch out for

Confirm histamine intolerance before chronic use; it is usually porcine-derived

What is it

Diamine oxidase (DAO) is the main enzyme that breaks down dietary histamine in the gut. Supplemental DAO, usually derived from porcine kidney, is used by people with histamine intolerance to help degrade histamine in food.

Is it worth it for you?

Use this as a quick fit check, not a diagnosis.

Worth considering if…

You have confirmed histamine intolerance
You react to histamine-rich meals
You want short-term coverage for specific meals

Probably skip if…

You have nonspecific GI or allergy symptoms without confirmed histamine intolerance
You avoid pork-derived products
You expect an all-day effect from one dose

Evidence at a glance

histamine intolerance symptoms

Limited Evidence
Effect
Modest in selected patients
Best fit
People with confirmed low DAO activity and histamine intolerance
Time
Within the meal

Evidence for 1 use

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

histamine intolerance symptoms

Supplement benefit
Limited Evidence

Supplemental DAO adds enzyme activity in the small intestine to degrade dietary histamine, and small trials suggest symptom benefit in people with confirmed histamine intolerance. The effect is short-lived and has not been shown for general, nonspecific symptoms.

Effect size
Modest in selected patients
Time to effect
Within the meal
Best fit
People with confirmed low DAO activity and histamine intolerance
Less likely
People with nonspecific symptoms and no confirmed histamine intolerance

Bottom line: Helpful for some people with confirmed histamine intolerance, taken before histamine-rich meals.

SourceYacoub et al., 2018 — PubMed

How it works

DAO oxidatively deaminates histamine to imidazole acetaldehyde, reducing the amount of intact histamine reaching circulation. People with low endogenous DAO activity may experience headaches, flushing, GI symptoms, and skin reactions after histamine-rich foods. Supplemental DAO taken before meals adds enzyme activity in the small intestine. Small trials suggest symptom benefit in selected populations with confirmed histamine intolerance, but not in general nonspecific symptoms.

How to take it

1. Typical dose
One capsule (around 4,200–30,000 HDU) per at-risk meal
2. Timing
15–30 minutes before a histamine-rich meal
3. With food
Just before food
4. How long to try
Use per meal; redose with each at-risk meal

What to track

Headache, flushing, GI, or skin reactions after meals
Which foods still trigger symptoms

1 commercial form

Compare the main delivery options and what they’re best suited for.

Porcine kidney-derived DAO

Enteric-coated capsules are the standard.

Acts locally in the gut; enteric coating used to protect activity through the stomach.

Safety

Know the common side effects, key cautions, and who should avoid it.

Common side effects

Generally well tolerated

Who should avoid it

  • People avoiding pork-derived products
  • Those with pork allergy (rare)

Pregnancy & breastfeeding

Limited data on supplemental DAO; endogenous DAO rises substantially in pregnancy, so supplementation is generally unnecessary.

Interactions

MAOIs, some antibiotics, and alcoholModerate

These can further reduce endogenous DAO activity; supplementation does not replace addressing them

Choosing a product

What to look for on the label — and what to be skeptical of.

Look for…

Stated DAO activity in HDU per capsule
Disclosed source (e.g., porcine kidney)
Enteric or pre-meal dosing guidance

Be skeptical of…

Cures all food intolerances
Eliminates allergies
Lets you eat any food

Frequently asked questions

Will DAO cure histamine intolerance?⌄

No. It can reduce symptoms after histamine-rich meals but does not address the underlying cause.

Is it vegetarian?⌄

Most DAO supplements are porcine-derived. Plant-derived DAO products exist but are less common.

References by claim

histamine intolerance symptoms

Yacoub et al., 2018 — PubMed (2018) link

Track Diamine Oxidase with Pilora

Set up dose reminders, check interactions, and join the community in the Pilora iPhone app.

Coming to App Store
Evidence-based·Last reviewed May 30, 2026·Evidence current as of May 30, 2026·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.