Sodium hydrogen sulphite
A sulphite preservative that releases sulphur dioxide to stop spoilage. Must be declared on UK labels as a major allergen above 10mg/kg.
Can trigger asthma attacks, wheezing and difficulty breathing in people with sulphite sensitivity, which affects between 5 and 13% of people with asthma. EFSA's 2022 review found that at high dietary exposure, intake of sulphites may exceed levels considered acceptable, and withdrew the previous safe intake threshold pending better data.
What is it?
Sodium hydrogen sulphite (also called sodium bisulphite) is an inorganic sodium salt that releases sulphur dioxide when dissolved in food. It belongs to the sulphite group of additives (E220-E228), all of which are assessed together because they share the same active compound, sulphur dioxide.
What does it do?
Sulphur dioxide released by E222 acts as both an antimicrobial agent and an antioxidant. It disrupts microbial enzymes, preventing bacteria, yeasts and moulds from growing. It also inhibits polyphenol oxidase, the enzyme responsible for browning in cut fruit and vegetables. In wine and beer, it controls fermentation and prevents oxidation that would turn the drink vinegary.
Where you will see it
Found in dried fruits such as apricots, raisins and sultanas, where it preserves colour and prevents mould. Also used in wine, beer and cider, some burger meats and breakfast sausages with cereal content, processed shrimp to prevent blackspot discolouration, fruit juices, pickled vegetables, and ready-made sauces and soups. On a label it appears as 'sodium hydrogen sulphite', 'sodium bisulphite', or 'E222', usually followed by the word 'sulphites' in bold as a mandatory allergen declaration.
What the science says
Asthma and airway reactions
Sulphites, including those released by E222, can provoke bronchospasm in people with asthma. When sulphite-containing food or drink is consumed, sulphur dioxide is released and can irritate the airway lining, triggering the cholinergic reflex that causes airways to narrow. The reaction is dose-related and more common in people with poorly controlled asthma. Allergy UK estimates that between 5 and 13% of people with asthma have sulphite sensitivity.
Sulphite inhalation and ingestion can cause bronchospasm in asthmatic patients through sulphur dioxide irritation of the airway mucosa and reflex bronchoconstriction, with reactions occurring at very low concentrations.
Between 5 and 13% of people with asthma are estimated to have sulphite sensitivity, with reactions ranging from wheezing and chest tightness to severe bronchospasm.
Sulphites as a mandatory allergen under UK food law
Sulphur dioxide and sulphites are one of the 14 major allergens requiring mandatory bold declaration on UK food labels. The threshold for declaration is 10mg per kg or per litre of finished product, expressed as sulphur dioxide equivalent. This means even small amounts must be labelled if they remain in the product.
Sulphur dioxide and sulphites at concentrations above 10mg/kg or 10mg/L must be declared in bold on UK food labels under the Food Information Regulations. Sulphites are one of the 14 major allergens recognised in UK law.
EFSA's 2022 safety review: ADI withdrawn, safety concern at high intake
EFSA's 2022 follow-up re-evaluation of all sulphites (E220-E228), including E222, found that the toxicity database was insufficient to set a formal safe intake level. The previous temporary acceptable daily intake of 0.7mg SO2 equivalent per kilogram of body weight per day, set in 2016, was withdrawn. EFSA instead applied a margin of exposure approach, and found that estimated dietary intakes fell below the minimum acceptable margin for most population groups, indicating a potential safety concern at high consumption levels.
The EFSA Panel on Food Additives and Flavourings withdrew the temporary group ADI for sulphites and concluded that dietary intake could be a safety concern for high consumers, including children aged 3 to 10 whose estimated intakes potentially exceeded acceptable levels.
EFSA identified a lower neurotoxicity reference point of 38mg SO2 equivalents per kilogram body weight per day based on prolonged visual evoked potential latency in rats, substantially lower than the 70mg/kg reference point used in 2016.
Genotoxicity: no concern found
Despite the broader safety concerns flagged in 2022, EFSA concluded that sulphites, including E222, do not raise a concern with respect to genotoxicity. This finding was consistent with an earlier assessment by ECHA in 2021 that found insufficient evidence for mutagenicity classification.
The EFSA Panel concluded that the use of sulphur dioxide and sulphites as food additives does not raise a concern with respect to genotoxicity, consistent with ECHA's 2021 assessment.
Nervous system effects in animal studies
The key reason EFSA tightened its safety assessment in 2022 was new data on neurological effects. Animal studies showed that oral sulphite intake prolonged the latency of visual evoked potentials, an early sign of slowed nerve signal transmission. This endpoint became the basis for EFSA's revised reference point, replacing the previous gastrointestinal endpoint. The relevance of this finding to humans at food-additive exposure levels is uncertain.
Ingested sulphites prolonged visual evoked potential latency in rats, indicating slowed nerve signal transmission, and this effect was dose-related and observed in both normal and sulphite-oxidase-deficient animals.
Visual evoked potential latency was prolonged in sulphite-exposed rats in a dose-dependent manner, providing the critical neurotoxicity endpoint used by EFSA in its 2022 re-evaluation.
Where it stands with the regulators
Who should be careful
People with asthma should be aware that sulphites can trigger bronchospasm, even at low doses. People with a confirmed sulphite intolerance or sensitivity should avoid foods containing 'sulphites', 'sulphur dioxide', 'sodium hydrogen sulphite', or any of E220 through E228 listed in bold on the ingredients label. People taking sulphite-sensitive medications or with sulphite oxidase enzyme deficiency are particularly vulnerable.
The honest read
Sulphites have a long regulatory history and are among the most studied food additive groups. The 2022 EFSA re-evaluation did not find a genotoxicity concern. However, EFSA withdrew its existing safe intake threshold because the toxicity data were judged insufficient to set a reliable one, and its margin of exposure calculations showed that estimated intakes for some high consumers, particularly children, may exceed levels considered acceptable. The primary concern driving that decision was a nervous system endpoint seen in animal studies. Regulators have not changed permitted food uses yet, but the assessment remains open and further data have been requested from industry. The link between sulphites and asthma attacks is well established in clinical observation. The extent to which the animal neurotoxicity findings apply to humans eating foods containing sulphites at permitted levels is genuinely uncertain, and that uncertainty is the honest state of the science.
Related additives
Common questions
Is E222 banned in the UK?
No. Sodium hydrogen sulphite (E222) is approved for use in the UK as a preservative under the assimilated version of EU Regulation 1333/2008. It is permitted in a range of foods including dried fruit, wine, beer, some processed meats and crustaceans. It cannot be used in fresh unprocessed meat or raw fruit and vegetables.
Did EFSA say sulphites were unsafe in 2022?
EFSA's 2022 re-evaluation concluded that dietary intake of sulphites 'could be a safety concern' for high consumers and withdrew the previous temporary acceptable daily intake because the toxicological database was insufficient to set a reliable figure. EFSA did not call for a ban, but flagged that estimated intakes for some groups, especially children, fell below the minimum margin considered acceptable. The review remains ongoing.
What foods contain E222?
E222 is most commonly found in dried apricots, raisins and other dried fruits, wine, beer and cider, some burger meats and sausages with a cereal content, processed shrimp, pickled vegetables, and ready-made sauces and soups. It appears on labels as 'sodium hydrogen sulphite', 'sodium bisulphite' or 'E222', usually with 'sulphites' highlighted in bold.
Is E222 vegan?
E222 itself is a synthetic inorganic salt with no animal-derived ingredients. However, some of the foods that commonly contain E222, such as wine, may be processed using animal-derived fining agents (separate from the sulphite additive). Vegans should check the full label or contact the manufacturer if they want confirmation about the entire product.
Sources
- UK FSA: Authorised food additive E222 Sodium Hydrogen Sulphite
- UK FSA: Approved additives and E numbers
- EFSA Journal 2022: Follow-up re-evaluation of sulphur dioxide and sulphites (E220-E228)
- PMC full text of EFSA 2022 sulphites follow-up opinion
- EFSA Journal 2016: Scientific Opinion on the re-evaluation of sulphur dioxide and sulphites (E220-E228)
- EFSA Supporting Publication 2025 (EN-9754): Update of dietary exposure to sulphur dioxide and sulphites with alternative maximum levels
- Allergy UK: Sulphites and Airway Symptoms factsheet
- Ozsoy et al. (2016): Effect of ingested sulphite on visual evoked potentials in rats, Toxicology and Industrial Health
- PubMed: Visual evoked potentials in normal and sulfite oxidase deficient rats exposed to ingested sulfite (2005)
- Food Navigator: Dietary intake of sulfites 'could be a safety concern' EFSA (2022)
- FSAI: Sulphur Dioxide and Sulphites permitted uses
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