E-numbers / Other additives / E515
also: Potassium sulphate · Potassium sulfate · Potassium hydrogen sulphate · E515(i)
Inorganic potassium salts used to control acidity and stabilise texture. One sub-form releases sulphite compounds, relevant to people with sulphite sensitivity or asthma.
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The bisulphate sub-form (E515ii) releases sulphite in solution, which can trigger breathing difficulty or asthma attacks in sulphite-sensitive individuals.
Why it’s worth knowing. The bisulphate sub-form (E515ii) releases sulphite in solution, which can trigger breathing difficulty or asthma attacks in sulphite-sensitive individuals.
E515 covers two related potassium salts: potassium sulphate (E515i) and potassium hydrogen sulphate, also called potassium bisulphate (E515ii). Both are inorganic mineral salts derived from sulphuric acid neutralised with potassium hydroxide or potassium carbonate. They appear as white crystalline powders and dissolve readily in water.
Acts primarily as an acidity regulator, keeping the pH of a food product stable. Also functions as a carrier or diluent for other food additives and flavourings, and can serve as a flour treatment agent. Potassium bisulphate (E515ii) is mildly acidic and releases hydrogen ions in solution, which can convert to sulphite species, giving it mild antimicrobial properties at the concentrations used.
Most commonly found in wine and brewing (acidification of grape must), baking powder formulations, flour treatment, some hard cheeses, seasoning blends, and as a carrier for flavourings. On a UK food label it appears as 'potassium sulphate', 'potassium hydrogen sulphate', or 'E515'.
Potassium hydrogen sulphate (E515ii) releases sulphite species when dissolved in water. Sulphites are established triggers for asthma and hypersensitivity reactions in sensitive individuals, including wheezing, chest tightness, and anaphylaxis in severe cases. This is why sulphites above 10 parts per million must be declared on UK food labels. E515i (the neutral sulphate) does not generate sulphite in the same way.
Sulphites are recognised as a cause of asthma exacerbations and allergic-type reactions in sensitive individuals, with the response being more pronounced in people with underlying asthma.
UK food labelling law requires declaration of sulphites and sulphur dioxide when present above 10mg/kg in the final food, reflecting the established hypersensitivity risk.
Both sub-forms contribute potassium to the diet. At typical food additive use levels this is nutritionally trivial for healthy people. For individuals with impaired kidney function, however, excess potassium from all dietary sources, including additives, can accumulate and contribute to hyperkalaemia, a raised blood potassium level that affects heart rhythm. No specific concern at normal food use levels has been established by regulators for the general population.
People with chronic kidney disease are advised by clinical guidelines to monitor total potassium intake from all food sources, including potassium-containing additives.
People with sulphite sensitivity or sulphite-induced asthma should be aware that products containing E515ii (potassium hydrogen sulphate) may contribute to sulphite exposure. On a label, look for 'E515', 'potassium hydrogen sulphate', or 'potassium bisulphate'. People managing chronic kidney disease should factor E515 into their total potassium monitoring.
For the majority of people, potassium sulphates at food additive levels are a minor and unremarkable part of the diet. The science is clear that the neutral sulphate sub-form (E515i) does not carry a sulphite concern. The bisulphate sub-form (E515ii) does generate sulphite species, and that is a real, well-established concern for people with sulphite sensitivity or asthma. The potassium load question is genuinely relevant only for people with kidney disease, where clinical guidance already addresses total dietary potassium. No carcinogenicity, endocrine disruption, or developmental concerns have been raised for this additive by any major regulatory body.
No. E515 (potassium sulphates) is approved for use in the UK under the assimilated EU Regulation 1333/2008, carried into UK law after Brexit. It remains on the UK FSA approved-additives list.
Potentially, if the product contains the bisulphate sub-form (E515ii). This form releases sulphite compounds in solution. Sulphites are a known asthma and hypersensitivity trigger. If sulphites are present above 10mg/kg in the finished food, UK law requires them to be declared on the label. If you have sulphite sensitivity, check for 'sulphites' or 'sulphur dioxide' in the allergen declaration as well as 'E515ii' or 'potassium hydrogen sulphate' in the ingredients.
E515 is most commonly used in wine and winemaking (to adjust acidity), baking powders, flour treatment preparations, some hard cheeses, and as a carrier for food flavourings and other additives. It is less common in everyday packaged foods than some other acidity regulators.
Yes. Both sub-forms of E515 are inorganic mineral salts with no animal-derived components. They are suitable for vegan and vegetarian diets.
Last reviewed: 20 June 2026
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