What is it?
Potassium metabisulphite is a white crystalline salt made by reacting sulphur dioxide with potassium carbonate. In food or drink it releases sulphur dioxide, which does the preserving. It is made in a factory, with nothing from animals.
E-numbers / Preservatives / E224
Potassium metabisulphite
also: Potassium metabisulfite · E224 · potassium pyrosulphite · Campden tablets
The sulphite winemakers add at the crusher and before bottling. It is behind most "contains sulphites" on wine, and it can set off asthma.
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Grapes, Acidity Regulator (Tartaric Acid), Preservatives (Sulphur Dioxide, Potassium Metabisulphite), Dried Egg White, Packaging Gas (Carbon Dioxide).
E224
Potassium metabisulphite
Sulphites can cause airway tightening, wheezing, hives and anaphylaxis in sensitive people, particularly those with asthma.
VeganVegetarian
260
of the 43,325 UK supermarket foods we checked declare E224 in their ingredients
That is 0.6%, counted by its code or its name.
Only 15% of these labels print “E224”. Most use the name: look for “potassium metabisulphite”.
Counted by NutraSafe from UK supermarket ingredient lists, September 2026. How we counted
How common it is in UK food, by aisle
- Alcoholic drinks147 products7.9% of 1,857
- Sauces, dressings and condiments36 products1.3% of 2,776
- Bread and bakery19 products0.5% of 3,682
- Soft drinks and juices15 products0.6% of 2,627
What potassium metabisulphite is, what it does and where you will see it
Why it’s worth knowing. Sulphites can cause airway tightening, wheezing, hives and anaphylaxis in sensitive people, particularly those with asthma. European reviewers withdrew the daily limit in 2022 after finding a possible nervous system concern in animal studies. In the lab, sulphites also slow the growth of helpful gut bacteria at strengths allowed in food.
What does it do?
The sulphur dioxide it releases stops bacteria, yeasts and moulds growing, and mops up oxygen to prevent browning and spoilage. In winemaking it is the main preservative, added when the grapes are crushed and again before bottling.
Where you will see it
Mainly wine, cider, beer and fruit juices. Also dried fruit (especially apricots, raisins and sultanas), pickled vegetables, jams, potato products such as instant mash and frozen chips, some shellfish, and some sauces and condiments. Labels call it potassium metabisulphite or E224, or declare "contains sulphites" or "sulphur dioxide".
What the science says
Linked to cancer and type 2 diabetes in large French studies
In 2026 two NutriNet-Santé analyses of more than 100,000 French adults reported that people who ate more sulphites had 12% more cancer overall, and that potassium metabisulphite itself was linked to a higher risk of type 2 diabetes. These are observational studies: they show links, not proof that the additive causes the disease.
Among 105,260 French adults followed for an average of 7.5 years, higher intake of sulphites as a group was linked to a 12% higher risk of cancer overall.
2026Observational study in peopleHasenböhler et al., The BMJ, NutriNet-Santé cohort
Among 108,723 French adults followed from 2009 to 2023, with 1,131 new cases of type 2 diabetes, potassium metabisulphite (E224) was one of 12 preservatives individually linked to a higher risk of type 2 diabetes.
2026Observational study in peopleNature Communications, NutriNet-Santé cohort
Sulphite sensitivity and asthma
In people with asthma, sulphites can tighten the airways within minutes of eating or drinking them. Suggested reasons include sulphur dioxide reaching the airways and setting off a nerve reflex, low levels of the enzyme that breaks sulphite down, and release of histamine or other inflammatory chemicals. Reactions range from wheezing and a tight chest to anaphylaxis. In one challenge study with potassium metabisulphite capsules, 3.9% of people with asthma reacted, and more of those on steroids.
Swallowing potassium metabisulphite capsules made 3.9% of people with asthma lose more than 20% of their lung function within 30 minutes. The rate was higher in people on steroids for asthma, the most sensitive group.
1986ObservationalPrevalence of sensitivity to sulfiting agents in asthmatic patients, American Journal of Medicine 1986, volume 81, 816-820, PMID 3535492
Sulphite reactions in people with asthma include airway tightening, wheezing, breathlessness, hives, swelling and, rarely, anaphylactic shock. The mechanism is not fully understood and probably involves several routes.
2014ObservationalConsiderations for the diagnosis and management of sulphite sensitivity, PMC4017445
Everyone with asthma who reacted to swallowed sulphite also reacted to breathed-in sulphite, and reacting to breathed-in sulphite was more common.
1985ObservationalInhaled metabisulfite sensitivity, PubMed PMID 3977136
Reviewers withdrew the daily limit in 2022
In 2022 European reviewers concluded the toxicity data were not enough to keep a firm daily limit for the sulphite group, E220 to E228, which includes E224. They withdrew the temporary 2016 limit of 0.7mg per kg of body weight. Using a margin-of-exposure approach, they found that high consumers in most age groups, including children aged 3 to 10 and adults, had margins below their threshold of 80. Teenagers were the only group where the margin stayed acceptable.
Reviewers withdrew the temporary shared limit for sulphites (E220 to E228) in 2022 because the toxicity data were inadequate. They switched to a margin-of-exposure approach based on a slowed eye-to-brain nerve signal in rats, with a reference point of 38mg per kg of body weight a day.
2022Regulator reviewEFSA Panel on Food Additives and Flavourings, EFSA Journal 2022, volume 20, 7594, doi:10.2903/j.efsa.2022.7594
Margins of exposure were below 80 for high consumers in every age group except teenagers, pointing to a possible safety concern for children aged 3 to 10 and adults.
2022Regulator reviewEFSA Panel on Food Additives and Flavourings, EFSA Journal 2022, volume 20, 7594, doi:10.2903/j.efsa.2022.7594
In 2016 reviewers had already found estimated sulphite intake over the temporary limit of 0.7mg per kg of body weight in every group surveyed, and asked for more toxicity studies.
2016Regulator reviewEFSA Panel on Food Additives and Flavourings, EFSA Journal 2016, volume 14, 4438, doi:10.2903/j.efsa.2016.4438
Nervous system signals in animal studies
The main effect behind the 2022 concern was a slower nerve signal from the eye to the brain in rats given sulphite in their water, an early sign of the nervous system not working well. Rats low in the enzyme that breaks sulphite down were more affected, which may reflect people whose enzyme is less active. There are no equivalent studies in people.
Rats given 25mg of sulphite per kg of body weight in their water had slower eye-to-brain nerve signals and more fat damage in brain and eye tissue. The effects were stronger in rats low in sulphite oxidase.
2005Animal studyYargicoglu et al., Neurotoxicology 2005, volume 26, 749-757, PMID 16150492
In older rats, sulphite slowed eye-to-brain nerve signals, more so at higher doses, and changed antioxidant enzymes in the brain, with the biggest effects in rats low in sulphite oxidase.
2016Animal studyOzsoy et al., Toxicology and Industrial Health 2016, volume 32, 1197-1207, PMID 25342669
Gut bacteria in the lab
At strengths within the range allowed in food, sulphites slowed or killed four kinds of helpful gut bacteria in lab experiments. No human trials have tested whether this happens with real diets.
Sulphites slowed the growth of Lactobacillus casei, Lactobacillus plantarum, Lactobacillus rhamnosus and Streptococcus thermophilus at 250 to 500ppm, and killed them at 1,000 to 3,780ppm, strengths within the range allowed in food.
2017Lab studyIrwin et al., PLOS ONE, doi:10.1371/journal.pone.0186629
It destroys vitamin B1
Sulphite splits the thiamine molecule, leaving vitamin B1 the body cannot use. That is why sulphites are not allowed in foods that are major sources of it. In wine, which is not a meaningful source of thiamine, this is not a nutritional problem, but the chemistry is established.
Sulphite splits thiamine at the bridge between its two rings, leaving the vitamin inactive, and does so faster in acidic conditions.
1984Lab studyDwivedi and Arnold, Food Chemistry, doi:10.1016/0308-8146(84)90101-8
Where it stands with the regulators
Approved in the UK and the EU
Daily limit. None set. The temporary shared limit of 0.7mg per kg of body weight was withdrawn in 2022 because the toxicity data were inadequate, and risk is now judged by margin of exposure.
- Legal basis
- On the Food Standards Agency's approved list for England, Scotland and Wales. Sulphur dioxide and sulphites (E220 to E228) are also one of the 14 allergens UK law makes labels declare, above 10mg per kg or per litre of sulphur dioxide.
- Permitted foods
- Wine and grape must · Cider, perry and fruit wines · Beer · Fruit juices and concentrates · Dried fruit and vegetables · Jams and marmalades · Potato products, including frozen chips and instant mash · Shellfish · Pickled and preserved vegetables · Biscuits and dry baking · Sauces, condiments and vinegar
- Maximum levels
- Depends on the food, 10 to 2,000mg per kg or per litre, measured as sulphur dioxide. Wine is typically 150mg per litre for dry red and 200mg per litre for dry white or rosé, and higher for sweet wines. Dried fruit can reach 2,000mg per kg. Allergen labelling applies above 10mg per kg or per litre.
- History
- European reviewers looked at the sulphite group in 2016, set a temporary limit, noted that intake in every group surveyed was already over it and asked for more studies. In 2022 they concluded the data were still inadequate, withdrew the limit and flagged a possible concern for high consumers in most age groups, based on nervous system signals in animals. Maximum levels in food have not yet been lowered following the 2022 opinion.
Who should be careful
People with asthma should be especially careful, as sulphites can cause anything from mild wheezing to life-threatening airway spasm, particularly in steroid-treated or poorly controlled asthma. Anyone known to be sensitive to sulphites should avoid foods and drinks showing "contains sulphites", sulphur dioxide or any of E220 to E228. The biggest sources are wine, dried fruit and processed potato products, and reactions usually start within 15 to 30 minutes. Our allergen checker looks for sulphites in the ingredient data behind a barcode, which helps most on wine and dried fruit where they are concentrated. The pack itself is the final word.
The honest read
E224 and its fellow sulphites are among the most studied preservatives and have been used since ancient times. The well-established risk is sulphite sensitivity in people with asthma: recorded, declarable under UK law and sometimes severe. The 2022 decision to withdraw the daily limit, because the data could not support one, is a meaningful regulatory signal. The nervous system findings behind it come from animal studies, and the gap between those doses and normal human intake has not been bridged by human evidence. Whether regular sulphite intake at normal levels affects gut bacteria or the nervous system in the general population is still open. In 2026 a large French study also linked sulphites as a group to 12% more cancer. It is observational, so it shows a link rather than proof.
Common questions about potassium metabisulphite
Is E224 banned in the UK?
No. Potassium metabisulphite is approved in the UK. It must be declared as an allergen when total sulphur dioxide is above 10mg per kg or per litre.
Why was the daily limit for sulphites withdrawn in 2022?
European reviewers concluded the toxicity data were not enough to keep a firm limit. Animal studies found nervous system effects, and intake surveys showed high consumers in most age groups were already over the previous temporary limit. They flagged a possible safety concern and called for more data, but did not recommend a ban.
What foods contain E224?
Wine and cider most often. Also dried fruit such as apricots and sultanas, potato products such as frozen chips and instant mash, beer, fruit juices, jams, pickles and some shellfish. Look for potassium metabisulphite, E224 or "contains sulphites".
Is E224 vegan?
Yes. It is a mineral salt made in a factory from sulphur dioxide and potassium carbonate, with nothing from animals.
Sources
- EFSA Panel on Food Additives and Flavourings: Follow-up of the re-evaluation of sulphur dioxide (E220) and sulphites (E221-E228) as food additives, EFSA Journal 2022;20(12):7594
- EFSA Scientific Opinion on the re-evaluation of sulphur dioxide (E220) and sulphites (E221-E228) as food additives, EFSA Journal 2016;14(4):4438
- UK FSA: Potassium metabisulphite (E224) regulated product entry
- UK Food Standards Agency: Approved additives and E numbers
- Anaphylaxis UK: Sulphites fact sheet
- Prevalence of sensitivity to sulfiting agents in asthmatic patients, American Journal of Medicine 1986, PMID 3535492
- Irwin et al. (2017): Sulfites inhibit the growth of four species of beneficial gut bacteria, PLOS ONE, doi:10.1371/journal.pone.0186629
- Yargicoglu et al. (2005): Visual evoked potentials in normal and sulphite oxidase deficient rats exposed to ingested sulphite, Neurotoxicology, PMID 16150492
- Ozsoy et al. (2016): The effect of ingested sulphite on visual evoked potentials, lipid peroxidation and antioxidant status of brain in normal and sulphite oxidase-deficient aged rats, Toxicology and Industrial Health 32(7):1197-1207, PMID 25342669
- Considerations for the diagnosis and management of sulphite sensitivity, PMC4017445
- UK FSA: Food allergen labelling and information requirements guidance
- Hasenböhler A et al. (2026) Intake of food additive preservatives and incidence of cancer: results from the NutriNet-Santé prospective cohort, The BMJ
- (2026) Associations between preservative food additives and type 2 diabetes incidence in the NutriNet-Santé prospective cohort, Nature Communications
Last reviewed: 20 June 2026
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