Histamine intolerance is the name given to symptoms that appear when the body seems to break down histamine from food too slowly, letting it build up and act on the skin, gut, airways and blood vessels. The usual explanation is a shortfall of diamine oxidase, or DAO, the enzyme that clears histamine in the gut. It is not an allergy and it cannot cause anaphylaxis. It also has no validated test, on the NHS or privately, and the evidence behind it is thinner than most pages on the subject suggest. This guide covers how the mechanism is thought to work, the symptoms and foods usually involved, what the research does and does not show, and how the question is approached in the UK.
How is histamine intolerance thought to work?
Histamine is a chemical the body makes and uses every day, in immune responses, stomach acid production and nerve signalling. It also occurs naturally in food, especially food that has been aged, fermented or stored for a long time, because bacteria produce histamine as they work on protein. The enzyme that deals with histamine arriving from food is diamine oxidase, which sits in the lining of the gut. A 2007 review that still anchors this field set out the proposed mechanism. If DAO activity is low, histamine from a meal passes into the body unbroken, where it can produce symptoms that look like an allergic reaction without any allergy being present.
The mechanism is plausible, but it rests on fewer controlled studies than its popularity suggests. The same 2007 review called for properly blinded feeding studies, and nearly two decades later most of that work has still not been done.
Histamine intolerance is not a food allergy. No IgE antibody is involved, symptoms build with the amount eaten rather than being set off by a trace, and the reaction cannot close airways. Knowing how a food allergy differs from an intolerance matters here, because hives, swelling or any change to your breathing after food is an allergy question for your GP, never something to investigate at home. Histamine intolerance is also different from histamine poisoning, where spoiled oily fish such as tuna or mackerel contains so much histamine that anyone eating it becomes unwell, whatever their enzyme levels, as a 2020 review of the field explains.
What are the symptoms of histamine intolerance?
The symptoms reported are wide-ranging. Flushing of the face and chest, headaches and migraine, an itchy or blotchy rash, a blocked or runny nose, bloating, cramps, diarrhoea and nausea appear most often in the 2007 review's list, with palpitations, dizziness and tiredness also described. Unlike an allergic reaction, they tend to build over minutes to hours and depend on how much histamine arrived in the meal.
The breadth of that list is itself a problem. The symptoms sit in several body systems at once, and every one of them has other, more common explanations. Bloating, cramps and diarrhoea after meals overlap with the symptoms of a food intolerance generally, and other types of food intolerance can produce a similar picture through entirely different mechanisms. Headaches have dozens of triggers, and flushing and rashes can be skin conditions in their own right. A pattern that spans meals, days and body systems is the hardest kind of pattern to pin to a single cause, which is one reason this diagnosis is contested.
Which foods are high in histamine?
Histamine rises as food ages, ferments or ripens. The foods most consistently named are matured cheeses, cured and processed meats such as salami, fermented foods such as sauerkraut and soy sauce, wine and beer, vinegar, yeast extract, and tinned, smoked or long-stored fish. Freshness matters more than the food itself in some cases, because histamine keeps forming as food sits, and neither cooking nor freezing destroys what has already formed.
Beyond that core, the published food lists disagree with each other. A 2021 analysis compared ten low-histamine diets from the scientific literature and found that fermented foods were the only category all ten excluded. Around a third of the excluded foods could be justified by their measured histamine content. Many of the rest, including citrus fruits and bananas, were banned as so-called histamine liberators, foods said to trigger the body's own histamine release through a mechanism the authors note has never been properly demonstrated. Two lists can disagree about tomatoes, spinach or chocolate while both calling themselves low-histamine. If you have been handed two contradictory lists, that is the state of the science, not carelessness.
How strong is the evidence?
Weaker than most pages about histamine intolerance suggest. A guideline from the German, Austrian and Swiss allergy societies, updated in 2021, is direct about the gaps. Reactions to food are reported far more often than they can be verified, a reliable laboratory test is missing, and when people with suspected histamine intolerance have been given histamine in blinded tests, their symptoms have often failed to reproduce. The guideline does not conclude that the symptoms are imagined. It concludes that blanket histamine bans run ahead of the evidence, and that assessment should be personal, staged and professionally supervised.
A 2024 systematic review of trials on natural food chemicals reached a similar position from a different direction. Across the 21 studies it examined, the clearest support for a low-histamine diet was in chronic urticaria, a long-term hives condition, where symptoms did improve. For gut symptoms, the evidence was too limited to draw firm conclusions. The 2020 review of the field reached the same conclusion, that more evidence is needed before the condition can be clearly defined, diagnosed and managed. Nobody can even say how common histamine intolerance is, because counting cases needs a test that does not exist.
Better answers are on the way. A double-blind, placebo-controlled trial registered in Barcelona in 2024 is testing a low-histamine diet and DAO supplements in 400 people over three months, the first study of anything like that size in this condition. Its results will carry more weight than everything published so far.
Can a test diagnose histamine intolerance?
No test can currently diagnose histamine intolerance, on the NHS or privately.
Private clinics sell blood tests that measure DAO, on the logic that a low level confirms the condition. The 2021 guideline assessed serum DAO measurement and found it inconclusive, because the level of DAO in blood has not been shown to reflect DAO activity in the gut, where histamine from food actually arrives. A 2024 Swedish study followed 18 people with histamine intolerance through a low-histamine diet and a normal diet in turn, and their blood DAO levels did not move consistently with either, even though symptoms improved during the low-histamine weeks. The cut-off many DAO tests use to declare a deficiency traces back to a 2015 report on 14 patients, whose authors themselves wrote that properly controlled studies were still needed.
The NHS does not test for histamine intolerance. The NHS food intolerance page names histamine among the ingredients people can react to, and the route it describes runs through your GP, who can rule out conditions with similar symptoms and refer you to a dietitian. The assessment there is a supervised period avoiding suspect foods followed by reintroduction, to see whether symptoms track the food. There is no equivalent here of the hydrogen breath test that supports a lactose intolerance diagnosis. That slow, unglamorous process is what currently identifies histamine intolerance, in the UK and everywhere else.
Our IgG-based food intolerance test does not test for histamine intolerance either. The reaction involves no antibodies, so no IgG result, ours included, can confirm it or rule it out, and the test does not measure histamine or DAO. What the panel measures is IgG antibodies to over 200 foods, and an elevated result may indicate a food sensitivity, which is a different kind of reaction. Its place is narrow. If a supervised low-histamine trial changes nothing, the question becomes which foods, if any, your body is reacting to, and an IgG result can offer a shortlist to take into structured removal and reintroduction with our clinical team or a registered dietitian. It is a starting point for that process, never a diagnosis of anything, histamine intolerance included.
Should you try a low-histamine diet?
Not on your own, and not indefinitely. The approach the 2021 guideline recommends runs in stages. A short period, around two to four weeks, of reducing high-histamine foods with guidance from a dietitian, then a stepwise reintroduction to find how much you can comfortably manage, then the least restrictive everyday diet that keeps symptoms away. The aim is a personal threshold, not a permanent ban.
The reasons for keeping it short and supervised are practical. Low-histamine lists cut across whole food groups, and restriction on that scale risks nutritional shortfalls and can entrench anxiety about foods that were never the problem. The reintroduction step is also the only part that actually tests the idea, and it is the step people skip when working alone. If restrictive eating has ever been a problem for you, speak to your GP or a registered dietitian before changing your diet at all.
DAO supplements, capsules taken before meals to top up the enzyme, are sold widely. The team behind the Barcelona trial counted around twenty studies of low-histamine diets and DAO supplements, most of them small, short and without control groups, which is why their trial exists. The supplements are sold as food supplements rather than medicines, and no standard dose has been established, so speak to a pharmacist before spending money on them.
When should you see a GP?
Some situations take this question out of self-management altogether.
- Any reaction to food that has ever involved swelling, widespread hives or a change to your breathing. That history makes allergy the first question, and it belongs with your GP, not a home experiment of any kind. Call 999 at the time if someone's lips, tongue or throat swell, they struggle to breathe, or they become faint or drowsy after eating
- Flushing, palpitations or diarrhoea that keeps returning. Each has causes beyond food that a GP should rule out before any diet change
- Blood in your stools, weight loss you cannot explain, a bowel habit that has changed for more than three weeks, trouble swallowing, vomiting that keeps going, gut symptoms starting for the first time after 50, or bowel or ovarian cancer in your family. A GP rules these out before food gets the blame
- Any suspected food reaction in a child. Children's diets are never restricted without advice from a GP, health visitor or paediatric dietitian
One more point sits naturally with a pharmacist. Some prescribed medicines can slow the body's breakdown of histamine. Never stop or change a prescribed medicine because of a suspected histamine problem. Raise it with your GP or pharmacist, who can look at your prescription as a whole.
This guide is for information only and does not replace medical advice. Speak to your GP or pharmacist about your own symptoms.
Sources
- Maintz L, Novak N (2007). Histamine and histamine intolerance. The American Journal of Clinical Nutrition. PubMed | DOI
- Reese I, Ballmer-Weber B, Beyer K, et al. (2021). Guideline on management of suspected adverse reactions to ingested histamine. Allergologie Select. PubMed | DOI
- Comas-Basté O, Sánchez-Pérez S, Veciana-Nogués MT, et al. (2020). Histamine Intolerance: The Current State of the Art. Biomolecules. PubMed | DOI
- Sánchez-Pérez S, Comas-Basté O, Veciana-Nogués MT, et al. (2021). Low-Histamine Diets: Is the Exclusion of Foods Justified by Their Histamine Content? Nutrients. PubMed | DOI
- Cooke Z, Lynam K, Tuck C, Trakman GL (2024). Naturally Occurring Food Chemical Components and Extraintestinal and Gastrointestinal Symptoms in Adults: A Systematic Review. Clinical and Experimental Allergy. PubMed | DOI
- Rentzos G, Weisheit A, Ekerljung L, van Odijk J (2024). Measurement of diamine oxidase (DAO) during low-histamine or ordinary diet in patients with histamine intolerance. European Journal of Clinical Nutrition. PubMed | DOI
- Manzotti G, Breda D, Di Gioacchino M, Burastero SE (2015). Serum diamine oxidase activity in patients with histamine intolerance. International Journal of Immunopathology and Pharmacology. PubMed | DOI
- Duelo A, Sánchez-Pérez S, Ruiz-Leon AM, et al. (2024). Study Protocol for a Prospective, Unicentric, Double-Blind, Randomized, and Placebo-Controlled Trial on the Efficacy of a Low-Histamine Diet and DAO Enzyme Supplementation in Patients with Histamine Intolerance. Nutrients. PubMed | DOI
- NHS. Food intolerance. nhs.uk
