Food additive intolerance means a reaction to something added to food, such as preservatives, colours, sweeteners and flavour enhancers, and confirmed cases are far rarer than most people expect. When people who believe additives affect them swallow those additives without knowing it, only a small minority react, and population studies put confirmed intolerance below one person in several hundred. The clear exception is sulphites, the preservatives in wine, dried fruit and many processed foods, which can trigger real and sometimes serious reactions, mainly in people with asthma. MSG carries a fifty-year reputation that blinded studies have largely failed to confirm. No test on sale anywhere can detect an additive reaction, and additives are not among the 270 foods and drinks our food intolerance test measures. This guide covers the evidence for sulphites, MSG, sweeteners, emulsifiers and colours, and how to approach a suspected additive reaction safely.
Sulphites can set off asthma attacks and allergic-type reactions, so any reaction that involves your breathing is a medical question, not a food-diary one. Call 999 if someone wheezes severely, struggles to breathe, their lips, tongue or throat swell, or they become faint or drowsy after eating or drinking. If anything like that has ever happened to you, see your GP before investigating any food or additive at home. Telling a food allergy from an intolerance is a job for a GP and an allergy clinic, and sulphur dioxide and sulphites sit on the UK's list of 14 regulated allergens for exactly that reason.
What are food additives and E numbers?
Food additives are substances added to food during manufacturing to preserve it, colour it, sweeten it, stabilise it or deepen its flavour. Every additive permitted in the UK has been through a safety assessment and carries an E number, E220 for sulphur dioxide and E621 for monosodium glutamate among them, and ingredients lists must name each one by its function and its name or number. That paper trail makes additives easier to track than almost any other suspected trigger, and the Food Standards Agency's guide to food additives sets out the categories and the approval system.
Additives are a separate question from the chemicals food produces by itself. The amines that build up in aged and fermented foods and the salicylates found in most plant foods are natural compounds, not additives, and each has its own guide.
How common is food additive intolerance?
Additive reactions are far rarer than people believe. In a British population study of 15,000 households, around 20 in every 100 people said they reacted to at least one of eight commonly blamed foods and ingredients, but when volunteers were challenged with the suspects disguised, so that nobody knew what they were swallowing, the confirmed rate across the population was nearer 1 or 2 in 100. The same gap between perception and confirmed reaction appears throughout this field.
For additives specifically, the confirmed numbers fall lower still. A review of the population studies estimated confirmed additive intolerance at somewhere between 1 in 700 and 1 in 3,000 adults, with a British estimate lower again at around 1 in 4,000. The one group with meaningfully higher rates was children with eczema and other allergic conditions, at 1 to 2 in 100, where an additive was usually aggravating an existing condition rather than creating a new one. Reactions to foods themselves, through the mechanisms that explain how a food intolerance works, are far more common than reactions to anything added to them.
What are the symptoms of food additive intolerance?
The symptoms separate into two broad groups, and which group matters depends on the additive. Sulphites mainly affect breathing. In sensitive people, nearly always people with asthma, they can trigger wheezing, chest tightness and asthma attacks, and reported reactions also include flushing, hives, stomach pain and diarrhoea, according to a review of the challenge studies.
Most other suspected additive reactions show up in the gut, as bloating, wind or loose stools. In many of those cases the cause is a poorly absorbed sweetener fermenting in the bowel rather than anything the immune system is doing, and the headaches and flushing reported after MSG rarely survive blinded testing. Symptoms that appear within minutes of eating, or that involve swelling or breathing, belong to allergy rather than intolerance and need a GP.
What are the symptoms and triggers of sulphite sensitivity?
Sulphites are preservatives that stop food discolouring and spoiling. Wine, beer and cider, dried fruit, sausages and burgers, fruit juice drinks and pickles are the main dietary sources, and any prepacked food or drink containing more than 10 milligrams per kilogram or litre must declare sulphites as an allergen on the label, under the UK's allergen labelling rules. That makes sulphites one of the few suspected triggers you can check from the packet alone.
The reactions are real, and most of the people who get them have asthma. The same review of the challenge studies found that between 3 and 10 in every 100 people with asthma react to swallowed sulphites, usually with wheezing and chest tightness, and that people with severe or steroid-dependent asthma are most at risk. Sulphites appear in some medicines as well as in food and drink. Outside asthma, reactions are described but far less common and far less studied. If you have asthma and have noticed wheezing after wine, dried fruit or cured meats, take the pattern to your GP or asthma nurse rather than testing it on yourself, because the next reaction cannot be assumed to match the last one.
What does the research show about MSG intolerance?
Monosodium glutamate is the sodium salt of glutamic acid, an amino acid found in nearly every protein we eat, and it is an authorised additive in the UK and across Europe, banned in neither. Its reputation is another matter, and it has carried one since the late 1960s, when symptoms after a Chinese restaurant meal were first described in a medical journal and the idea spread long before anyone tested it properly.
The largest blinded test is a multicentre study of 130 people who believed they reacted to MSG, given MSG and identical dummy capsules in turn. Large doses taken on an empty stomach did produce more symptoms than the dummy, but the reactions were infrequent, inconsistent, and did not repeat when the same people were retested. Given with food, MSG produced no response at all. An earlier trial of 61 self-described MSG-sensitive adults found much the same, with roughly a third reacting to a large plain dose of MSG on the first round and a quarter reacting to the dummy drink, a difference small enough to be chance, although symptom scores ran somewhat higher after MSG.
The symptom-specific research points the same way. A Cochrane review could find only two blinded trials of MSG in people with asthma, 24 adults in total, and neither found any effect on breathing. For headaches, one distinction does the work. A review of dietary headache triggers rated MSG dissolved in drinks among the better evidenced provocation triggers, while a systematic review of the same trials found that studies giving MSG with food showed no difference from placebo, and that high-dose MSG solutions have a recognisable taste, so several of the positive studies were probably not blinded in practice.
A 2025 review weighed the research accumulated since and concluded that blinded studies rarely confirm consistent symptoms at the doses found in real meals, and that true allergy to MSG appears vanishingly rare. A large dose of MSG on an empty stomach may produce symptoms in some people. Normal amounts eaten in food have never been convincingly shown to.
How do food additives affect gut health?
Artificial sweeteners are where additive research is currently most active, because of what they may do to gut bacteria. In a randomised trial of 120 healthy adults, two weeks of saccharin, sucralose, aspartame or stevia, at doses below the official daily limits, measurably changed the mix of gut bacteria, and saccharin and sucralose also worsened blood sugar control in some participants, with the effect varying from person to person. An earlier trial of 34 adults found that a week of high-dose sucralose changed neither blood sugar nor gut bacteria. The evidence here is mixed, it concerns blood sugar and the microbiome rather than intolerance symptoms, and none of it shows sweeteners causing bloating or diarrhoea at normal intakes.
Sugar-free sweets and gums are the exception, and the mechanism is not an additive reaction. Polyol sweeteners such as sorbitol are poorly absorbed and ferment in the bowel, which in quantity causes wind and loose stools through the same fermentation route as the FODMAP family of fermentable carbohydrates.
Emulsifiers, which stop processed foods separating, are under similar scrutiny. In a small controlled feeding study, seven healthy adults ate a deliberately high daily dose of the emulsifier carboxymethylcellulose for 11 days, reported slightly more abdominal discomfort than the comparison group, and finished with less variety in their gut bacteria. This is early research in a handful of people, and it concerns long-term gut health rather than meal-by-meal symptoms, so it is a reason to watch the field rather than a reason to fear an ingredients list.
Food colours carry the strongest regulatory response. A UK trial of 297 children from the general population found that drinks containing mixes of artificial colours and the preservative sodium benzoate produced a small average increase in hyperactive behaviour, rated by parents, teachers and trained observers. The effect was modest and varied widely between children, and the study measured behaviour across groups, not anything about any one child. It is the reason six colours now carry a mandatory warning on UK labels, that they may have an adverse effect on activity and attention in children, and the reason most UK manufacturers have replaced them. Any concern about a child's behaviour or diet belongs with a GP or health visitor, and a child's food is never restricted at home over a suspected additive.
How can you identify a suspected food additive reaction?
The pattern matters more than any single episode, because an additive crosses food groups. A real sulphite reaction should follow wine, dried apricots and cured sausages, foods with little else in common, while symptoms that follow one food but spare other products containing the same additive point at the food rather than the additive. UK ingredients lists do a large part of the work here, since every additive must be named and sulphites above the labelling threshold are flagged as allergens.
Confirming a suspicion is a supervised job. A UK review of additive and food chemical sensitivity, written by NHS allergy dietitians, supports removing a single suspected additive for a limited period in selected people, on the condition that other explanations have been checked first and that the additive is deliberately brought back afterwards, because reintroduction is the only step that tests the idea. The same review warns that removing several additives at once quickly turns into removing most processed foods and many ordinary ones, with a real risk of nutritional shortfall, above all in children. Plan any trial of this kind with our clinical team or a registered dietitian, and if restrictive eating has ever been difficult ground for you, involve your GP before changing anything.
Is there a test for MSG or additive intolerance?
No. Additives are not foods, and no additive appears on our panel. Sulphite reactions in asthma run through the airways, and MSG symptoms, where they occur at all, involve no antibody, so there is no IgG signal for any test to measure. No test on sale anywhere can confirm or rule out an additive reaction, and a result claiming to show an MSG or sulphite intolerance is claiming something the science cannot support.
Our food-specific IgG test measures the IgG antibodies your blood carries against 270 individual foods and drinks, and an elevated result may indicate a food sensitivity to that specific food. In an additive question, that answers one particular half of the puzzle. If one processed food keeps causing trouble, the additive and the food itself are both suspects, and checking other products that contain the same additive only examines one of them. An elevated IgG result against an ingredient of that food, wheat or yeast, say, moves the investigation onto the food itself, while a panel showing nothing elevated leaves the additive question open for the supervised route above. Our clinical team reads results with that additive-or-ingredient distinction in mind.
Whichever way the evidence points, the confirming step is the same. A structured period of avoidance followed by deliberate reintroduction, planned with our clinical team or a dietitian, is what turns a suspicion about an additive or a food into an answer.
When should you see a GP about a suspected additive reaction?
See your GP, rather than starting a food experiment, if you have asthma and have noticed wheezing or chest tightness after wine, beer, dried fruit or processed meats, because a sulphite pattern in asthma needs proper assessment and your asthma plan may need adjusting. Any reaction that has ever involved swelling, widespread hives or difficulty breathing is a 999 call at the time it happens and an allergy question for your GP afterwards. For gut symptoms, book an appointment before changing your diet if you have blood in your stool, unexplained weight loss, a change in bowel habit lasting more than three weeks, difficulty swallowing, vomiting that keeps returning, the constant tiredness of iron-deficiency anaemia, new gut symptoms over the age of 50, or bowel or ovarian cancer in your close family. And concerns about additives and a child, whether about behaviour or gut symptoms, go to a GP or health visitor, never into a restricted diet at home.
This guide is for information only and does not replace medical advice. Speak to your GP or pharmacist about your own symptoms.
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