Histamine, sulphites and food additives: what is known about reactions

Some people feel unwell after a glass of wine, a plate of aged cheese, or a handful of dried apricots, and histamine, sulphites or other additives often get the blame. Some of these reactions are real and well described. Others are harder to pin down, and many of the tests sold to identify them are unreliable. Here is what health services and allergy specialists say, how to read labels, and why to get advice before you cut foods out.

Intolerance or allergy?

A food intolerance is when you have difficulty digesting certain foods or ingredients, the UK's National Health Service (NHS) explains. Symptoms usually start a few hours after eating and commonly include diarrhoea, bloating, farting and tummy pain. A food allergy is different: it involves the immune system and can cause itchy skin, wheezing, or swelling of the lips, face and eyes.

The NHS lists histamine, sulphites, monosodium glutamate (MSG) and benzoates among the things some people are intolerant to. Intolerances are usually not dangerous, but the Australasian Society of Clinical Immunology and Allergy (ASCIA), the professional body for allergy specialists in Australia and New Zealand, notes an exception: reactions to sulphites and benzoates can, rarely, be severe.

What is histamine intolerance?

Histamine is a natural chemical that the body makes and that is also found in food. According to Allergy UK, the UK's national allergy charity, it forms when proteins in food break down, particularly during fermentation, ageing or spoilage. Most people tolerate the amounts in a typical diet, but some report symptoms after even small amounts.

Those symptoms usually appear 30 minutes to a few hours after eating, Allergy UK says, and can include headaches, flushing, itching or hives, a blocked or runny nose, wheezing, a fast heartbeat, feeling sick, tummy pain and diarrhoea. Foods it lists as high in histamine and similar substances include red wine, beer and cider, aged cheeses, cured meats, fermented foods, canned or smoked fish, and some fruit and vegetables such as tomatoes, spinach and citrus fruit.

How certain is the evidence?

Less certain than many websites suggest. One theory is that some people break down histamine from food more slowly, and Allergy UK links this to low activity of an enzyme in the gut. A 2021 guideline from the German, Swiss and Austrian allergy societies, however, calls the evidence for a link between histamine in food and reproducible symptoms "limited and contradictory", and says the role of this enzyme has not been proven. The guideline also notes that:

• there are no reliable laboratory tests to confirm or rule out the diagnosis, and measuring the enzyme in the blood has no diagnostic value;
• in one study, 39 of 56 people with suspected histamine intolerance reacted when they knew they were being given histamine, but none of those reactions could be reproduced in a blinded test against a dummy drink (placebo);
• the histamine content of the same food varies enormously, from almost none to 2,000 mg per kilogram in samples of Emmental cheese, so food lists based on histamine content are a poor guide.

Sulphites and asthma

Sulphites (also spelled sulfites) are preservatives that stop food and drink spoiling or changing colour by releasing a gas, sulphur dioxide. Allergy UK and ASCIA list common sources: wine, beer and cider; dried fruit such as dried apricots; bottled lemon and lime juice, vinegar and pickles; some soft drinks; processed potato products, sauces and packet soups; and processed meat products and prawns.

True sulphite allergy is very rare, Allergy UK says. Most people affected have a sensitivity or intolerance, with symptoms within a few minutes to an hour, such as headache, flushing, a runny nose, cough, tummy pain, diarrhoea or a mild rash.

Breathing symptoms are the most common reaction, according to ASCIA, which estimates that about 5 to 10 in 100 people with asthma react with wheezing, chest tightness or coughing. Allergy UK puts the figure at under 2 in 100 people overall and between 5 and 13 in 100 people with asthma, and names people whose asthma needs steroid treatment as most at risk. Reactions are more likely when asthma is poorly controlled. Breathing in sulphur dioxide can narrow the airways, ASCIA explains, which may be why some people react quickly to wine or beer.

If you have asthma and notice symptoms after foods or drinks like these, tell your doctor. Allergy UK advises keeping asthma well controlled and checking medicines, some of which contain sulphites; a pharmacist can check for you. It also stresses that although some adrenaline auto-injectors contain sulphites, adrenaline should always be given as prescribed in an emergency. There are no reliable blood or skin tests for sulphite reactions, ASCIA notes; diagnosis may involve a food challenge supervised by an allergy specialist.

Other common additives

Additives are put mainly into processed foods to keep them safe, make them last longer, or change their taste, texture or appearance, the World Health Organization (WHO) explains, and most unprocessed foods contain none. Each one is assessed for safety before it is approved, internationally by an expert committee run by WHO and the Food and Agriculture Organization of the United Nations, and by national authorities.

• Monosodium glutamate (MSG). A flavour enhancer; glutamate also occurs naturally in tomatoes and cheese. The US Food and Drug Administration (FDA) considers added MSG safe: in studies of people who describe themselves as sensitive, scientists could not consistently trigger reactions. An expert review for the FDA found that some sensitive people may get short-lived, mild symptoms after 3 grams or more taken without food; a typical serving contains less than 0.5 grams.
• Benzoates. Preservatives found in soft drinks, fruit juices, jams and pickles, the NHS says. ASCIA notes that they have been reported as asthma triggers.
• Sweeteners ending in "-ol". Sorbitol, xylitol and similar sweeteners in some sugar-free sweets and chewing gum can add to gas, according to the US National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Our guide to FODMAPs explains why.

Reading labels

Most countries follow international standards that require manufacturers to list the additives in their products, WHO says, and people with sensitivities should check labels carefully. Rules differ between countries, but a few patterns help:

• E numbers. In the European Union, sulphites appear as E220 to E228, and Allergy UK also lists E150b, caustic sulphite caramel. In Australia and New Zealand, ASCIA notes, the same codes appear without the "E".
• Sulphites as an allergen. In the UK and the EU, sulphites must be declared above 10 mg per kilogram or per litre, including in loose and restaurant food, Allergy UK says. If in doubt, ask.
• MSG. In the US, added MSG must be listed as "monosodium glutamate", the FDA says, but ingredients such as yeast extract contain glutamate naturally and do not have to say so.

Why get a diagnosis before cutting foods out

• The NHS says not to cut foods out of your, or your child's, diet without the advice of a GP or dietitian, because you could miss out on important vitamins and minerals.
• Home tests that claim to diagnose food intolerances are not recommended, the NHS adds. ASCIA lists IgG food antibody tests, hair analysis and kinesiology among methods shown to be inaccurate and unreliable.
• Other conditions cause similar symptoms. The German, Swiss and Austrian guideline lists lactose intolerance, fructose malabsorption, coeliac disease and inflammatory bowel disease among those to look for first. Our guides to lactose intolerance and coeliac disease cover two of them.

If your doctor agrees that diet may be playing a part, ASCIA recommends a temporary elimination diet supervised by a dietitian and a doctor, then reintroducing foods under controlled conditions. For suspected histamine intolerance, Allergy UK describes cutting down high-histamine foods for 2 to 4 weeks, then bringing them back one at a time, ideally with a dietitian, while keeping a food and symptom diary. The aim, as the German, Swiss and Austrian guideline puts it, is to avoid diets that restrict people more than they need to.

When to see a doctor

See a GP if you or your child have symptoms of a food intolerance that keep coming back, the NHS advises. If you have asthma, also talk to your doctor if you notice wheezing, chest tightness or coughing after particular foods or drinks.

Call your local emergency number if your lips, mouth, throat or tongue suddenly swell; you are breathing very fast or struggling to breathe; your throat feels tight or you are struggling to swallow; your skin, tongue or lips turn blue, grey or pale; you suddenly become very confused, drowsy or dizzy; or someone faints and cannot be woken. The NHS warns that these can be signs of a serious allergic reaction. If you have been prescribed an adrenaline auto-injector, use it as prescribed.