In 1910, two Britons, Henry Dale and Patrick Laidlaw, described what a little-known chemical did in the body. It widened blood vessels, made them leak, and made smooth muscle tighten. They had found the body's own alarm bell: histamine. Like any alarm, it is wonderful until it will not stop ringing.
More than a century later, histamine sits at the centre of one of the most confusing labels in health. "Histamine intolerance" is blamed for headaches that come and go, hives, flushing, a blocked nose and an upset stomach, often after a meal that was fine last week. Some of us are sure we have it. Others have been told it does not exist.
The truth sits in between, and it is more useful than either side. Histamine reactions to food are real. The condition is harder to pin down than the internet suggests. And the thing that matters most is not a long list of forbidden foods, but how fresh your food is.
What histamine does
Histamine is not a villain. We make it on purpose.
It is stored in mast cells, which Paul Ehrlich named in the late 1870s after the large granules he saw inside them under the microscope. When the body senses a threat, those cells release histamine, and blood vessels widen and leak so the immune system can reach the trouble. That is why histamine brings redness, swelling and itching. It is a central player in itch. Every mosquito bite is a small histamine story.
Histamine has quieter jobs too. Cells in the stomach lining release it to help switch on stomach acid. And in the brain, it works as a messenger that keeps us awake, which is why the older antihistamines make people drowsy. Those drugs have their own history: in 1937, Daniel Bovet discovered the first antihistamines, medicines that block histamine's effects.
How the body clears it
The body breaks histamine down with two enzymes. Diamine oxidase, usually shortened to DAO, works mainly in the gut, and deals with the histamine that arrives in food. Histamine N-methyltransferase, or HNMT, works inside our cells. DAO is busiest in two places: the lining of the gut and the placenta. In pregnancy, cells of the placenta release DAO into the mother's blood.
The gut has its own histamine makers as well. Some gut bacteria, lactobacilli among them, can produce a substantial amount of it. So the histamine in our bodies comes from three places: our own cells, our food, and the bacteria living with us. We never quite eat alone.
When more histamine arrives than the enzymes can clear, it can spill over into symptoms. That is the idea behind histamine intolerance.
Is it real?
This is where honesty helps.
Reactions to histamine in food are accepted as real. But mainstream medicine does not recognise histamine intolerance as a separate condition that can be diagnosed. There is no specific test that can confirm it. Estimates suggest it affects around 1% of people, though nobody can be sure, precisely because it is so hard to diagnose.
The symptoms put down to it are wide-ranging: flushing, hives and itching; headaches, dizziness and twitching; stomach cramps. None of them is specific. Each can come from something else. Our bodies use the same few words for many different stories. And the evidence linking histamine eaten in food to these symptoms is still limited and inconsistent.
One small test shows why the picture is so murky. Ten healthy women with no food intolerance drank, without knowing which, either plain peppermint tea or the same tea with an amount of histamine found in ordinary meals. Five of them reacted to the histamine, with diarrhoea, wind, headache, itching or a racing heart, some of them hours later. None reacted to the plain tea. A big enough load can unsettle anyone.
That does not mean you are imagining it. It means a label is less useful than a test of your own, which comes further down.
Where the histamine in food comes from
Most of the histamine in food is made by bacteria. Many foods contain histidine, an amino acid, and bacteria turn it into histamine as they grow.
Fish shows this most clearly. Tuna, mackerel and their relatives are rich in histidine. Left above about 16°C, the bacteria on them start turning that histidine into histamine. Enough of it causes scombroid poisoning: flushing, sweating, headache, itching and an upset stomach soon after eating. And once histamine has formed, cooking, smoking, canning or freezing will not destroy it. Properly cooked fish can still make you ill if it was kept warm for too long beforehand. Along with ciguatera, scombroid is one of the most common kinds of seafood poisoning, and sardines, anchovies and herring are among the usual culprits too.
The prevention is simple: fish should be chilled or frozen straight after it is caught, and kept cold until it is cooked.
Why freshness beats any list
Low-histamine food lists are everywhere, and they rarely agree. There is a good reason: the same food can vary enormously.
Take Emmental cheese. Its histamine content has been measured anywhere from under 0.1 to as much as 2,000 milligrams per kilo. That is a range of more than twenty-thousand-fold, in one kind of cheese. A list that calls a food "high" or "low" cannot capture that.
What a list cannot tell you, freshness can. Histamine builds as bacteria work, and bacteria work when food is warm and old. So the most reliable low-histamine diet is a fresh one: meat and fish bought fresh and cooked soon, or frozen straight away; eggs; plain food cooked and eaten while it is new. Fresh is the one rule that never contradicts itself.
Leftovers are where histamine creeps in. The Cooking Skills That Keep Your Family Healthy and Safe, linked below, has the rule that keeps them safe: cooked food into the fridge within two hours, in shallow containers so it cools quickly, eaten within a few days or frozen. Shallow cool quickly and go straight into the freezer.
The usual suspects
Some foods carry more histamine by their nature, because time and bacteria are part of how they are made.
Aged cheese builds histamine as it matures, though, as Emmental shows, the amount varies widely. Cured and fermented meats such as salami are made the same slow way. Some plants carry histamine of their own, tomatoes among them. Fermented foods in general are high in it: Are Fermented Foods Good for Your Gut?, linked below, has why every low-histamine diet cuts them. Wine and other drinks made by fermenting belong here too. Alcohol may matter in its own right: the reviewers who describe histamine intolerance also advise avoiding substances that raise histamine, alcohol among them, and medicines that block DAO. If you take a medicine every day, ask whether it affects DAO. And fish that has not been kept cold is the classic case.
Some lists go further and ban foods said to make the body release its own histamine, the so-called histamine liberators. There is no robust evidence that any food works that way. A food on such a list may still disagree with you for other reasons, but the liberator idea itself is still a theory. A tidy theory is not the same as a tested one.
Unexpected Causes of Your Headaches and How to Find Yours has the clue worth knowing: a headache that starts while you are still drinking wine, with flushing or a blocked nose, points to something in the drink, and histamine is a likely culprit.
The DAO capsule
If the gut enzyme clears histamine from food, could taking it as a capsule help? Two tests give a first answer.
In the first, 28 people with suspected histamine intolerance took DAO capsules before meals for four weeks. Every one of their symptoms improved, and when they stopped, the symptoms came back. But everyone knew they were taking the real thing, and there was no comparison group.
The second was stricter. A hundred people with migraine and low DAO levels were given either DAO or a dummy capsule for a month, without knowing which. With DAO, their attacks shortened from about 6.1 hours to 4.8. The dummy group's attacks shortened a little too, but not by enough to count.
So DAO capsules show early promise, especially before a meal you cannot control, like eating out. The evidence is small, and they do not fix whatever is behind the problem. A helper at the table, not a cure.
The test that works
Since no lab test can settle it, the best test is your own.
Keep a diary. For a few weeks, write down what you eat, how fresh it was, and any symptoms, with the time they started. If you have periods, note where you are in your cycle too.
Eat fresh for a while. Build meals on fresh meat, fish and eggs, cooked soon after buying or frozen straight away. Leave out aged cheese, cured meats, fermented foods, wine and leftovers.
Bring foods back one at a time. If symptoms ease, reintroduce one suspect at a time, a few days apart, and watch what happens. A food that brings symptoms back each time is telling you something. A food that does nothing can come back to the table.
This is slower than a test result. It is also the only result that is truly about you. For a fuller guide to eating this way, Janice Joneja's sets out the low-histamine diet and the step-by-step return of foods.
When it is not histamine intolerance
Some reactions are urgent, and the skin can give a clue. The rash of scombroid poisoning is usually flat, without the raised, swollen wheals often seen in a true allergy. Swelling of the lips, tongue or throat, trouble breathing, or feeling faint after eating can be a serious allergic reaction. Call your local emergency number.
Some foods cause trouble through other means. Are Fermented Foods Good for Your Gut?, linked below, has why aged cheese and other fermented foods can be dangerous for people on some antidepressants, because of a different compound, tyramine.
There is also a separate condition with a similar name. In mast cell activation syndrome, the mast cells themselves release histamine and other chemicals too readily, and the symptoms can run from gut trouble and long-lasting pain to full anaphylaxis. It is worth knowing the name if your reactions do not follow food at all.
And if symptoms are frequent or severe, get them looked at. Many conditions share the same signs.
Back to the alarm bell
Dale and Laidlaw found a chemical the body uses to sound the alarm. Dale went further: in 1936 he shared the Nobel Prize with Otto Loewi for showing that nerves pass their signals on with chemicals. The man who described histamine's alarm also showed how our nerves talk. Most of the time, it rings for good reason and stops when the job is done. For some of us, the food on the plate adds to the noise.
We cannot always measure that. But we can keep our food fresh, keep notes, and let our own bodies show us the pattern. An alarm is easier to live with once we know what sets it off.
This week, cook your fish and meat on the day you buy them, freeze what you will not eat, and write down how you feel.
Wondering which fermented foods are worth it? Are Fermented Foods Good for Your Gut? — what is live in the jar, whether the bacteria survive your stomach, and when fermented foods cause trouble.
Want the kitchen habits that keep food safe? The Cooking Skills That Keep Your Family Healthy and Safe — thawing in the fridge, cooling leftovers fast, and why cooking at home changes what we eat.
Know someone whose low-histamine list keeps changing? Send them this, and the cheese that varies twenty-thousand-fold.
Disclaimer: This article is general information. For advice about your own health, talk to a qualified health professional. Swelling of the lips, tongue or throat, trouble breathing or feeling faint after eating is an emergency: call your local emergency number. If you take antidepressants, check before eating aged or fermented foods.
Affiliate Disclosure: This article contains affiliate links. As an Amazon Associate, All For Life earns from qualifying purchases, at no extra cost to you. We only link to products we would recommend without the commission.
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