E-numbers / Preservatives / E227
also: Calcium bisulphite · Calcium bisulfite · INS 227
A sulphite preservative that stops spoilage and browning in processed foods, canned vegetables, and brewing.
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Sulphites can trigger bronchospasm and asthma attacks in people with sulphite sensitivity, particularly those with asthma.
Why it’s worth knowing. Sulphites can trigger bronchospasm and asthma attacks in people with sulphite sensitivity, particularly those with asthma. In 2022, EFSA found that high consumers of sulphite-containing foods may exceed levels at which nerve-signalling effects have been observed in animal studies.
Calcium hydrogen sulphite (also called calcium bisulphite) is an inorganic salt formed by combining calcium with bisulphite ions. It releases sulphur dioxide when it reacts with food or acid. It is one of eight sulphite additives (E220-E228) that are assessed as a group by regulators because they all deliver sulphur dioxide as the active agent.
It preserves food by releasing sulphur dioxide, which kills or slows the growth of bacteria, yeasts, and moulds. It also blocks enzymatic browning reactions that would discolour cut fruit and vegetables. The calcium component additionally firms the texture of canned vegetables by cross-linking pectin in the cell walls.
Used in canned and bottled vegetables, brined and preserved cherries, beer (to sanitise casks and prevent secondary fermentation), fruit juices, pickles, and some dried fruit products. On a UK label it appears as 'calcium hydrogen sulphite', 'calcium bisulphite', or 'E227'. Because sulphites are a major allergen under UK food law, products containing more than 10mg/kg must also carry a 'contains sulphites' or 'sulphur dioxide' declaration, usually in bold.
When sulphites meet stomach acid they generate sulphur dioxide gas, which travels up to the airways and can cause them to constrict. This is the best-established real-world concern. Sensitivity is concentrated in people who already have asthma: studies suggest 5 to 13 per cent of asthmatics react to sulphite exposure, compared with under 2 per cent of the general population. The reaction can include wheezing, chest tightness, and, in severe cases, an acute asthma attack within minutes of eating a sulphite-containing food.
Bronchoconstrictor responses to inhaled sodium metabisulphite were reproducible in 15 of 18 atopic subjects, and correlated with methacholine responsiveness, pointing to airway hyperresponsiveness as the underlying susceptibility factor.
Sulphite sensitivity in the general population is estimated at under 2 per cent, rising to 5 to 13 per cent in people with asthma.
In a 2022 follow-up assessment, EFSA's expert panel found animal evidence that high sulphite intake delayed nerve-signalling responses in the brain, an early marker of nervous system disruption. The panel withdrew the previous temporary acceptable daily intake because the toxicity data were inadequate to set a reliable limit. Instead it used a margin-of-exposure approach and found that calculated safety margins fell below the acceptable threshold for most population groups at high exposure levels, including children. EFSA called the situation a safety concern and asked for new toxicology data.
EFSA withdrew the temporary group ADI of 0.7 mg SO2 equivalents/kg body weight per day established in 2016 because the toxicity database was inadequate, and instead applied a margin-of-exposure approach with a benchmark dose lower confidence limit of 38 mg SO2 equivalents/kg body weight per day.
Margins of exposure were below 80 (the threshold used to indicate a safety concern) for most population groups at high dietary sulphite exposure levels, with children aged 3 to 10 potentially exceeding reference points by up to 12.5 per cent and adults by up to 60 per cent.
Animal studies showed a dose-dependent prolongation of visual evoked potential latency in sulphite-exposed rats, interpreted as an early sign of nervous system dysfunction and used as the critical endpoint for the 2022 EFSA risk assessment.
Sulphur dioxide and sulphites are one of the 14 major allergens that must be declared on UK food labels. Any product containing E227 at levels above 10mg/kg or 10mg/litre must carry an explicit statement. This is not an allergy in the classic IgE antibody sense but a sensitivity or intolerance that can cause significant respiratory and skin reactions in those affected.
Sulphur dioxide and sulphites are among the 14 allergens requiring mandatory declaration under UK food law. Emphasis on the label is required when present above 10mg/kg or 10mg/litre in the finished product.
People with asthma should be especially cautious, as sulphites can trigger breathing difficulties and attacks. People with a known sulphite sensitivity should also avoid foods containing it. Look for 'calcium hydrogen sulphite', 'calcium bisulphite', 'E227', 'sulphites', or 'sulphur dioxide' on the label, all of which indicate the presence of this group of additives. Our allergen checker looks for each of those names, since one additive printed three ways is easy to miss. The packet remains the final word.
The asthma and airway concern is well-established and is why sulphites carry a mandatory allergen declaration. The picture on broader toxicity is less settled: EFSA's 2022 assessment flagged a potential nervous-system signal at high intake but acknowledged the underlying animal data are limited and no new industry safety studies were provided. The agency has not recommended removing sulphites from the permitted list, but it has not been able to restore a firm acceptable daily intake either. The question of what high habitual intake means for human nervous-system health is not resolved.
No. E227 calcium hydrogen sulphite is permitted in the UK and EU as a preservative and firming agent under UK food additive law and assimilated EU Regulation 1333/2008. It is not banned. However, EFSA withdrew the acceptable daily intake in 2022 due to data gaps and the group remains under review.
Yes, in people with sulphite sensitivity. When sulphites encounter stomach acid they release sulphur dioxide, which can constrict the airways. Studies suggest 5 to 13 per cent of people with asthma react to sulphites. Reactions typically happen within minutes and can include wheezing, chest tightness, and breathing difficulty.
E227 is used in canned and bottled vegetables, preserved cherries, beer (particularly in cask cleaning), fruit juices, pickles, and some dried fruit. On a label it appears as 'calcium hydrogen sulphite', 'calcium bisulphite', or 'E227'. Products containing sulphites above 10mg/kg must also carry a 'contains sulphites' or 'sulphur dioxide' statement.
Yes. Calcium hydrogen sulphite is synthesised from mineral and chemical sources, with no animal-derived ingredients involved in its manufacture. It is suitable for vegans and vegetarians.
Last reviewed: 20 June 2026
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