Histamine Intolerance Supplement Guide

Supplements are heavily marketed for histamine intolerance. The evidence behind most of them is thin. This page sums up what is known, where the official safety limits are, and what to ask a pharmacist before you buy anything. It does not give doses: a safe amount depends on your medicines and health, and that is a conversation for your pharmacist or doctor.

Before you start. Talk to your doctor or pharmacist before taking any supplement, especially if you take prescription medicines, are pregnant or breastfeeding, are under 18, or have kidney or liver disease. Diet and a symptom log come first; many people need no supplements at all.

What the evidence says, supplement by supplement

DAO enzyme

Diamine oxidase (DAO) is the enzyme that breaks down histamine from food in the gut. Supplemental DAO is the most studied option, but the human studies are small trials and pilot studies, so the evidence is still limited. Most products are made from pig kidney, so they are not vegetarian. Ask a pharmacist whether it suits you and follow the product label. Our DAO enzyme supplements guide explains what to look for on the label.

Quercetin

Quercetin is a plant flavonoid. Lab studies suggest it can calm mast cells, but it has not been tested in people with histamine intolerance. It can interact with some medicines, so check with a pharmacist first. More in our quercetin guide.

Vitamin C

Vitamin C is often sold as a “DAO cofactor”. It is not one: DAO is a copper-containing enzyme whose cofactors are copper and TPQ, which is built into the enzyme. Vitamin C supplements have not been tested in histamine intolerance. The NIH upper limit for adults is 2,000 mg a day. See vitamin C and histamine intolerance.

Vitamin B6

The idea that B6 is an essential DAO cofactor comes from older lab data and is unproven. B6 is, however, the cofactor for histidine decarboxylase, the enzyme that makes histamine. High B6 intake can damage nerves: the NIH upper limit is 100 mg a day, EFSA set 12 mg a day in 2023, and Australia’s TGA says nerve problems can’t be ruled out below 50 mg a day. B6 is often hidden in magnesium, zinc and multivitamin products. If you stop a B6 supplement you chose yourself, that is fine; prescribed B6 is only changed by the prescriber. More in vitamin B6 and histamine intolerance.

Copper, zinc and magnesium

Copper is genuinely part of the DAO enzyme, but there is no evidence that copper supplements help histamine intolerance, and excess copper is harmful. Zinc is not a DAO cofactor, and too much zinc causes copper deficiency; the NIH upper limit is 40 mg a day. Magnesium has not been tested in histamine intolerance; the NIH upper limit is 350 mg a day from supplements.

Probiotics

Some gut bacteria can make histamine, and lab studies show that some strains do and others don’t. Lists of “histamine-safe” probiotic strains are theory, not established fact, and there are no good human trials in histamine intolerance. If you are immunocompromised, ask a doctor before taking any probiotic.

Other supplements

Nettle, NAC, luteolin, PEA, bromelain, curcumin and melatonin are all untested in histamine intolerance. Several interact with medicines, including blood thinners. SAMe and methylation products have no evidence in histamine intolerance; MTHFR gene variants are common and normal, and the CDC says carriers can take folic acid.

Medicine interactions to ask about

  • Magnesium: bisphosphonates, some antibiotics (tetracyclines, quinolones), diuretics, proton pump inhibitors.
  • Zinc: quinolone and tetracycline antibiotics, penicillamine, thiazide diuretics.
  • Vitamin C: some cancer treatments; statins taken with niacin.
  • Vitamin B6: some anti-seizure medicines, cycloserine, theophylline.

These examples come from the NIH Office of Dietary Supplements fact sheets. They are not a complete list, which is why a pharmacist check matters.

Questions to take to your pharmacist

  • Does this interact with anything I take, including the contraceptive pill and over-the-counter painkillers?
  • Is it safe in pregnancy or breastfeeding, or with my kidney or liver health?
  • Does another product I take already contain it?
  • What does the label say, and is that right for me?
  • How will I know whether it is helping? (Log it alongside your symptoms.)

Never stop a prescribed medicine on your own. If you have taken cetirizine or levocetirizine for a long time, ask your doctor or pharmacist before stopping: the FDA warns that stopping can cause severe itching.

When to see a doctor

See a doctor if you have unexplained weight loss, blood in your stool, persistent vomiting or diarrhoea, trouble swallowing, or symptoms that don’t improve on a low-histamine diet. Histamine intolerance has no validated lab test, so other causes such as coeliac disease, food allergy, IBS, inflammatory bowel disease and mast cell disorders need ruling out first.

Emergency signs. Swelling of the lips, tongue or throat, trouble breathing, wheeze or fainting after food can be anaphylaxis. Use an adrenaline (epinephrine) auto-injector if you have one and call emergency services. Antihistamines are not a substitute for adrenaline.

Sources: Maintz & Novak, Am J Clin Nutr 2007; Comas-Basté et al., Biomolecules 2020; NIH Office of Dietary Supplements fact sheets (vitamin C, vitamin B6, magnesium, zinc, copper); EFSA 2023 opinion on vitamin B6; TGA vitamin B6 safety update; CDC on MTHFR; FDA warning on cetirizine and levocetirizine. Reviewed October 2026 by the histamine.guide editorial team.

Medical disclaimer: This content is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before starting any supplement regimen.