Calcium hydrogen sulphite
A sulphite-type preservative that is not currently a permitted food additive in the UK or EU under Regulation 1333/2008.
The sulphite group of additives, of which this compound is a member, can trigger bronchoconstriction, asthma attacks, hives and, in rare cases, anaphylaxis in people sensitive to sulphites. Sulphites are one of the 14 major allergens under UK food law and must be declared on labels when the total sulphur dioxide in the finished product exceeds 10mg per kg.
What is it?
Calcium hydrogen sulphite is the calcium salt of sulphurous acid, also called calcium bisulphite. It is a greenish liquid with a pronounced sulphur odour. Chemically it belongs to the sulphite group of compounds (sulphur-containing inorganic salts), which also includes the approved food preservatives E220 to E228.
What does it do?
Like other sulphites, calcium hydrogen sulphite acts as a preservative and antioxidant. It inhibits the growth of bacteria, moulds and yeasts, and prevents oxidative browning in food. When used in beverages, it can prevent secondary fermentation. In the body, ingested sulphites are metabolised primarily by the enzyme sulphite oxidase, which converts them to sulphate for excretion. People with low activity of this enzyme, and people with asthma, are more likely to experience adverse reactions.
Where you will see it
The substance calcium hydrogen sulphite is not permitted as a food additive in the UK or EU under the current approved list. The closely related compound calcium hydrogen sulphite is permitted under E227, which appears in wine, beer, cider, dried fruits, potato products, fruit juices, pickled vegetables and seafood. If you see 'sulphites' or 'sulphur dioxide' on a label, that refers to the approved sulphite group (E220-E228), not specifically E229.
What the science says
Sulphite sensitivity and asthma
Sulphites as a class can cause bronchoconstriction and asthma exacerbations in susceptible people. The estimated rate of sulphite sensitivity in the general population is below 2%, but rises to 5-13% among people with asthma. Steroid-dependent asthmatics and those with severe airway hyperresponsiveness are at highest risk. The mechanism involves sulphur dioxide released in the airway activating both IgE pathways and cholinergic reflexes, though the precise mechanism remains under investigation.
Sulphite sensitivity affects an estimated 5-13% of people with asthma, who may experience wheezing, chest tightness, hives, nausea and, in rare cases, anaphylaxis following sulphite ingestion.
Sulphur dioxide and sulphites are one of the 14 major allergens under UK food law. Prepared foods containing sulphites at or above 10mg per kg (total SO2) must carry a declaration on the label in bold or capitals.
EFSA re-evaluation of the sulphite group and withdrawal of the ADI
EFSA re-evaluated the sulphite group (E220-E228) in 2016 and set a temporary group ADI of 0.7mg SO2 equivalents per kg of body weight per day. In 2022, after a follow-up review, EFSA withdrew this temporary ADI because the available toxicity data were insufficient to support it. Instead, EFSA applied a margin-of-exposure approach and found that estimated exposures among high consumers across all population groups fell below the safety margin considered adequate, indicating a potential concern for this subgroup. E229 is not included in EU Regulation 1333/2008 and was not in scope for either review.
The 2016 EFSA re-evaluation set a temporary group ADI of 0.7mg SO2 equivalents per kg body weight per day for E220-E228, pending additional toxicity data.
In the 2022 follow-up, EFSA withdrew the temporary ADI for sulphites (E220-E228) because the available toxicity database was inadequate to derive one. The margin-of-exposure analysis indicated a safety concern for high consumers across all population groups.
Regulatory status: not a permitted food additive in the UK or EU
The current approved list of food additives in the UK (UK FSA) and the EU (Regulation 1333/2008, Annex II) includes the sulphite preservatives E220 through E228 only. The number E229 does not appear on either list. The FSA approved-additives page moves directly from E228 (potassium hydrogen sulphite) to E234 (nisin), with no entry for E229. The EFSA re-evaluation of sulphites in 2016 and 2022 covered E220-E228 only, with E229 not in scope.
The UK FSA approved-additives list (as published on food.gov.uk) does not include E229. The preservative series lists E228 (potassium hydrogen sulphite) and then jumps directly to E234 (nisin). Verified by direct WebFetch of the live FSA page in June 2026.
EU Regulation 1333/2008 (Annex II), which is the legal basis for food additive permissions in Great Britain post-Brexit as assimilated law, does not list E229 as a permitted food additive.
Neurotoxic signals in animal studies for the sulphite group
Animal studies in the sulphite group re-evaluation identified neurotoxic signals, including prolonged visual evoked potential latency, which is an early marker of nervous system dysfunction. These findings were observed at exposures above the levels typical from food, and the relevance to human exposure from food is uncertain. The findings contributed to EFSA's decision to withdraw the ADI for the sulphite group.
Animal studies included in the EFSA 2022 follow-up review identified neurotoxic effects, specifically prolonged visual evoked potential latency, in sulphite-exposed animals. EFSA considered these findings relevant to the derivation of a health-based guidance value.
Where it stands with the regulators
Who should be careful
Anyone with sulphite sensitivity or asthma should treat E229 with the same caution as the approved sulphites (E220-E228). Since E229 is not permitted in UK or EU food, you should not encounter it on a UK food label. If a product lists 'sulphites' in bold or capitals, that refers to the approved sulphite group. People with asthma, particularly steroid-dependent asthmatics, are at greatest risk of adverse reactions to sulphites as a class.
The honest read
E229 is an E number assigned to calcium hydrogen sulphite that does not appear in the UK or EU approved food additives list. The sulphite preservative series recognised in UK food law runs from E220 to E228. The substance calcium hydrogen sulphite is used in food under the number E227. For the broader sulphite group (E220-E228), EFSA's 2022 re-evaluation found the available evidence insufficient to set an acceptable daily intake, and estimated that high consumers may exceed the level at which adverse effects cannot be excluded. Sulphite sensitivity, particularly bronchoconstriction in people with asthma, is a well-established and real-world concern for the group. The science on sulphite neurotoxicity from animal studies remains uncertain in terms of relevance to human food exposure.
Related additives
Common questions
Is E229 banned in the UK?
E229 is not listed as a permitted food additive in the UK FSA approved-additives register or in EU Regulation 1333/2008 (Annex II), which remains the basis for UK food additive law as assimilated legislation. The UK-approved sulphite preservative series runs from E220 to E228, with no E229 entry. It is therefore not authorised for use in food sold in the UK.
What is the difference between E229 and E227?
Both refer to calcium hydrogen sulphite (also called calcium bisulphite), the same chemical compound. E227 is the number used in the current UK and EU approved food additives framework. E229 is not recognised in either framework. If you see calcium hydrogen sulphite on a food label it will be listed as E227, not E229.
What foods contain E229?
Because E229 is not a permitted food additive in the UK or EU, it should not appear in foods sold here. The related compound calcium hydrogen sulphite (E227) is used in wine, beer, cider, dried fruits, potato products, fruit juices and seafood.
Is E229 vegan?
Calcium hydrogen sulphite is an inorganic mineral compound with no animal-derived ingredients. However, E229 is not a permitted additive in the UK or EU, so the question of its vegan status in food products does not apply in practice.
Sources
- UK Food Standards Agency - Approved additives and E numbers
- Regulation (EC) No 1333/2008 on food additives (EUR-Lex)
- EFSA ANS Panel - Scientific Opinion on the re-evaluation of sulfur dioxide (E 220) and sulphites (E 221-228) as food additives. EFSA Journal 2016;14(4):4438
- EFSA ANS Panel - Follow-up of the re-evaluation of sulfur dioxide (E 220) and sulphites (E 221-228). EFSA Journal 2022;20(12):7594. PMC9685353
- Vally H, Misso NLA. Adverse reactions to the sulphite additives. Gastroenterol Hepatol Bed Bench. 2012;5(1):16-23. PMC4017445
- Anaphylaxis UK - Sulphites fact sheet
- Allergy UK - Sulphites and Airway Symptoms factsheet
- UK Food Standards Agency - Food allergen labelling and information requirements technical guidance
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