E-numbers / Preservatives / E226
also: Calcium sulfite · E226
A calcium-based sulphite preservative that stops bacteria, mould and yeast growing in food and drink.
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Sulphites trigger breathing difficulties in around 5 to 13 percent of people with asthma.
Why it’s worth knowing. Sulphites trigger breathing difficulties in around 5 to 13 percent of people with asthma. EFSA withdrew its safety benchmark in 2022 because evidence suggests high-end dietary intake may exceed levels considered safe for most age groups.
Calcium sulphite is the calcium salt of sulphurous acid (CaSO3). It is a white powder that releases sulphur dioxide when it encounters heat or stomach acid, which is the active antimicrobial and antioxidant agent. It is synthetically produced and contains no animal-derived ingredients.
When calcium sulphite releases sulphur dioxide in food, that gas inhibits the enzymes bacteria and moulds need to reproduce, preventing spoilage. It also acts as an antioxidant, scavenging oxygen to stop cut or dried fruit browning and prevent oxidative degradation in wine and juice. In the body, sulphite is normally converted to sulphate by the enzyme sulphite oxidase and excreted in urine.
Most commonly used in dried fruits such as apricots, raisins and figs to preserve colour; in fruit juices and concentrates; in ciders and fermented grape-based drinks; in preserved and canned vegetables; and in some grain and meat products. On a label it will appear as 'calcium sulphite', 'E226', or more often as the group term 'sulphites' or 'sulphur dioxide and sulphites', printed in bold as a major allergen declaration.
Sulphites release sulphur dioxide gas when swallowed, which can travel into the airways and cause them to constrict. Somewhere between 5 and 13 percent of people with asthma experience wheezing, chest tightness or cough after eating foods with sulphites, with poorly controlled or steroid-dependent asthma carrying the highest risk. True IgE-mediated allergy is rare; most reactions are a sensitivity or intolerance rather than a classic allergic response.
Sulphite sensitivity causes bronchoconstriction, wheezing and dyspnoea primarily in asthmatics, with incidence estimated at 5 to 13 percent in that population versus under 2 percent in the general population.
The probable mechanism involves inhaled sulphur dioxide irritating already-reactive airways, activating both IgE pathways and cholinergic reflexes to cause bronchoconstriction.
In 2016 EFSA set a temporary acceptable daily intake for sulphites as a group (E220 to E228, including E226). In 2022, after reviewing further evidence, EFSA concluded the toxicity data were insufficient to confirm that limit and withdrew it. Using a margin of exposure approach with a benchmark dose of 38 mg sulphur dioxide equivalents per kilogram of body weight per day, based on delayed nerve response to visual stimuli in animals, the margin fell below the safety threshold of 80 for most population groups including children and adults under both refined and maximum-permitted-level exposure scenarios.
The EFSA Panel withdrew the temporary group ADI for sulphites (E220-E228) because no new toxicological data had been submitted and the existing database was judged inadequate to derive a reliable limit.
Using a margin of exposure approach, margins at the 95th percentile fell below 80 for all population groups except adolescents under a refined exposure scenario, raising a safety concern.
A 2025 EFSA dietary exposure update modelled alternative maximum levels to explore which permitted-level reductions would bring MOEs above 80 across population groups.
The key endpoint used to set the 2022 benchmark dose was prolonged visual evoked potential latency, a measure of how long nerve signals take to travel from eye to brain, observed in animal studies at higher sulphite exposures. This signal formed the basis for a lower, more conservative reference point than the one used in 2016. The relevance of this endpoint to human dietary exposure at typical levels has not been confirmed.
Prolonged visual evoked potential latency in animal models provided the basis for a benchmark dose of 38 mg SO2 equivalents per kilogram of body weight per day, lower than the previous 70 mg reference point.
The enzyme sulphite oxidase normally converts ingested sulphite to harmless sulphate for excretion. Individuals with low sulphite oxidase activity, including those with a rare inherited condition affecting this enzyme, may accumulate sulphite and react at lower exposures. The enzyme requires molybdenum as a cofactor, so molybdenum deficiency may also reduce its efficiency.
Sulphite oxidase converts sulphite to sulphate via a molybdenum-dependent reaction; individuals with reduced enzyme activity or molybdenum deficiency show heightened sensitivity to dietary sulphites.
UK food law requires that sulphites and sulphur dioxide must be declared on labels in bold or otherwise emphasised text whenever they are present at more than 10mg per kg or 10mg per litre in the finished product, expressed as sulphur dioxide. This is a legal requirement for all 14 major allergens and applies to pre-packed and non-pre-packed food alike.
Sulphites are one of the 14 major allergens under retained EU food law and UK Food Information Regulations; they must be emphasised on labels when present above 10mg/kg or 10mg/litre as SO2.
People with asthma should exercise caution, particularly if asthma is poorly controlled or steroid-dependent, as sulphites can trigger wheezing or breathing difficulties in 5 to 13 percent of asthmatics. Anyone with a known sensitivity to sulphites or sulphur dioxide should check labels for 'sulphites', 'sulphur dioxide and sulphites' or 'E226', which must appear in bold as a declared allergen when present above 10mg/kg. Where that bold declaration is in the ingredient data we hold, our allergen checker surfaces it on a scanned pack. Read the label too, our data can be out of date.
Sulphites are among the more scientifically scrutinised food additives. The EFSA story here is unusual: the agency set a safety limit in 2016, then formally withdrew it in 2022 not because new harms were discovered but because the industry provided no new toxicological data to shore up the limit. The 2022 assessment used a neurotoxicity endpoint from animal studies to set a reference point and found that estimated consumer intakes at the high end may fall uncomfortably close to, or below, the minimum acceptable safety margin for most age groups. That does not mean the additive is proven harmful at typical dietary exposures; it means regulators do not currently have enough data to confirm it is not. For people without asthma and without sulphite sensitivity, the science is genuinely unsettled and the regulatory picture remains open. For people with asthma, the link between sulphite intake and breathing reactions is well-documented.
No. E226 is a permitted food additive in the UK under the assimilated EU Regulation 1333/2008. However, EFSA withdrew its acceptable daily intake in 2022 after industry failed to provide the toxicological data needed to confirm it, and the safety review of sulphites as a group is ongoing.
Yes, in people with asthma. When sulphites are swallowed they release sulphur dioxide, which can irritate the airways and cause wheezing, chest tightness or cough. Estimates suggest 5 to 13 percent of people with asthma experience reactions. People with poorly controlled or steroid-dependent asthma are at highest risk.
Dried fruits such as apricots, raisins and figs are among the most common sources. It also appears in fruit juice concentrates, cider and fermented grape drinks, preserved vegetables, some baked goods, and certain sausages and meat products. On the label it will usually appear as 'sulphites' or 'sulphur dioxide and sulphites' in bold, or as 'E226' or 'calcium sulphite'.
Yes. Calcium sulphite is a synthetically produced mineral compound. It contains no animal-derived ingredients and is suitable for vegans and vegetarians.
Last reviewed: 20 June 2026
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