E-numbers / Preservatives / E225
also: Potassium sulfite · INS 225
A sulphite preservative that is not a permitted food additive in the UK or EU. Other sulphite forms (E220-E224, E226-E228) are approved in their place.
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E225 itself has no authorised use in UK or EU food, so encountering it on a UK label would be unlawful.
Why it’s worth knowing. E225 itself has no authorised use in UK or EU food, so encountering it on a UK label would be unlawful. As a sulphite compound, it would release sulphur dioxide in food, which can trigger breathing difficulties and asthma attacks in sensitive people. Sulphites as a class are one of the 14 declarable allergens under UK food law and must be listed on labels above 10mg/kg. It is not on the UK list of approved food additives, so you will not normally see this E number on a UK label.
Potassium sulphite (K2SO3) is an inorganic salt of sulphurous acid. It belongs to the sulphite family of compounds, which also includes sodium sulphite (E221), sodium metabisulphite (E223) and potassium metabisulphite (E224). All sulphites release sulphur dioxide when dissolved in water or acidic food environments.
Sulphites inhibit microbial growth by disrupting enzyme activity in bacteria, moulds and yeasts. They also act as antioxidants, blocking the enzymatic browning reactions that discolour cut fruit, wine and dried foods. Sulphites chemically cleave thiamine (vitamin B1), reducing its content in preserved foods. In the human body, sulphites are metabolised by the liver enzyme sulphite oxidase and excreted as sulphate.
Potassium sulphite (E225) is not authorised for use in UK or EU food products. The related permitted sulphites (E220-E224 and E226-E228) appear in wine, cider, beer, dried fruits such as apricots and raisins, fruit juices, seafood, vinegar-based products, sausages, and some bakery products. On UK labels, sulphites from any of these authorised sources must appear as 'sulphur dioxide' or 'sulphites' in the allergen-highlighted ingredients list when present above 10mg/kg.
Sulphites are among the most documented food triggers for asthma. When swallowed, sulphites produce sulphur dioxide gas in the acidic stomach environment; inhaling this during eating or drinking can cause rapid narrowing of the airways. Studies estimate that between 3% and 10% of people with asthma experience reactions when consuming sulphites. Those with steroid-dependent asthma or marked airway hyper-responsiveness face the highest risk. Reactions can range from coughing and wheezing to, rarely, life-threatening bronchospasm.
Between 3% and 10% of asthmatic subjects who consume sulphites experience sensitivity reactions, including wheezing, chest tightness and cough. Steroid-dependent asthmatics and those with marked airway hyper-responsiveness are at greatest risk.
The mechanism involves sulphur dioxide formation in the airways stimulating a cholinergic reflex causing bronchoconstriction; an IgE-mediated immune response has also been proposed, though the precise mechanisms remain incompletely understood.
EFSA's 2022 re-evaluation of permitted sulphites (E220-E224 and E226-E228) identified new evidence from animal studies of neurotoxic effects, including a delayed response of nerve cells to stimuli detected via visual evoked potential testing. EFSA found its toxicity database insufficient to set an acceptable daily intake (ADI) and withdrew the previous temporary group ADI of 0.7mg SO2 equivalent per kg body weight per day. Using margin-of-exposure (MOE) calculations instead, EFSA found MOEs below its safety threshold of 80 for most population groups at the 95th percentile of intake, raising a safety concern for high consumers. These findings apply to the sulphite class as a whole and inform the risk profile of all sulphite compounds including E225.
Animal studies supporting sulphite-induced neurotoxic effects, including prolonged visual evoked potential latency, led EFSA to withdraw the temporary group ADI. MOEs at the 95th percentile of dietary exposure were below 80 for all population groups except adolescents, raising a safety concern.
At high dietary exposure, estimated sulphite intakes for children exceeded the safety margin by up to 12.5% and for adults by up to 60%, based on margin-of-exposure analysis.
Sulphite ions chemically cleave the thiamine molecule, breaking it down and reducing its availability in preserved food. In wine containing 400ppm sulphur dioxide, around half the added thiamine was destroyed within one week under laboratory conditions. This is a chemical degradation effect in the food product itself, not a direct effect on the body's thiamine stores from normal consumption at food-additive levels.
The sulphite ion cleaves the thiamine molecule by adding to its pyrimidinium ring, producing degradation products that no longer function as vitamin B1. In wine at 400ppm SO2, approximately 50% of thiamine was destroyed within one week at pH 3.5.
E225 does not appear in Annex II of EU Regulation (EC) No 1333/2008 or on the UK FSA approved additives list. The permitted sulphites in UK and EU food law run E220, E221, E222, E223, E224, then jump to E226, E227 and E228. E225 was never granted authorisation under the current EU positive-list system and is absent from the UK's assimilated version of that regulation. Its use in food in Great Britain or Northern Ireland would be unlawful.
E225 (potassium sulphite) does not appear in Annex II of EU Regulation (EC) No 1333/2008 (as retained in UK law). The permitted sulphites are E220-E224 and E226-E228 only.
E225 is absent from the UK FSA approved additives and E numbers list.
The Miscellaneous Food Additives Regulations 1995 list sulphites E220-E224 and E226-E228; E225 does not appear.
Sulphite sensitivity does not involve the immune system in the same way as a classic food allergy, so most people who react are said to be intolerant rather than allergic. Symptoms include wheezing, hives, stomach pain, vomiting and worsening eczema. People with low levels of the enzyme sulphite oxidase may be less able to break down sulphites, causing them to accumulate and trigger airway tightening. Anaphylaxis from sulphites is very rare but has been reported.
Most sulphite reactions are sensitivity or intolerance responses not involving the immune system; symptoms range from respiratory (wheezing, tight chest) to skin (hives, worsening eczema) and gastrointestinal. A very small number of anaphylaxis cases have been reported.
Anyone with asthma or known sulphite sensitivity should watch for 'sulphur dioxide' or 'sulphites' on ingredients lists, which UK law requires to be declared in bold (or otherwise emphasised) when present above 10mg/kg in pre-packed food. Children with chronic asthma are at particular risk. E225 itself should not appear on any UK food label as it is not an authorised additive, so its presence would indicate a labelling irregularity.
E225 has no authorised role in UK or EU food, so UK shoppers are very unlikely to encounter it on a label. The broader picture for sulphites in UK food is that seven related compounds (E220-E224, E226-E228) are permitted and widely used, and their class-level safety is an active regulatory question. EFSA withdrew a temporary safety threshold in 2022 after animal studies showed early signs of nerve dysfunction and dietary modelling found high consumers, including children, may be exceeding safe exposure margins. The science is live, not settled: EFSA called for further data, the permitted compounds remain in use, and the debate about whether current maximum levels are appropriate is ongoing. People with asthma have the most direct and established reason to watch their sulphite intake from any source.
E225 (potassium sulphite) is not authorised as a food additive in the UK or EU. It does not appear on the UK FSA approved-additives list or in Annex II of EU Regulation (EC) No 1333/2008 as retained in UK law. Its use in UK food would be unlawful. Other sulphite compounds, E220 through E224 and E226 through E228, are authorised and widely used.
E numbers are codes assigned within a numbering system; having a code does not mean a substance is authorised for food use. E225 was assigned a number within the sulphite range (E220-E228) but was never granted authorisation under the EU positive-list system. Regulatory approval and code assignment are separate processes.
No foods in the UK or EU should legally contain E225, as it is not an authorised food additive here. The permitted sulphite preservatives (E220-E224, E226-E228) appear in wine, cider, beer, dried fruits, fruit juices, seafood products, sausages and some bakery products. On UK labels, any sulphite from these authorised sources must be declared as 'sulphur dioxide' or 'sulphites' when present above 10mg/kg.
Potassium sulphite is a synthetic inorganic compound with no animal-derived ingredients. As it is not authorised for food use in the UK or EU, the question of its presence in products does not arise in practice here.
Last reviewed: 20 June 2026
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