E224 · Antioxidants, Preservatives

Potassium metabisulphite

Moderate risk allergenpreservative

Sulphite allergen.

Category: Antioxidants, Preservatives
Acceptable daily intake: 0.7 mg/kg body weight/day (EFSA)
Vegan: Yes
Vegetarian: Yes

What it is

Potassium metabisulphite (E224) is a synthetic preservative and antioxidant. Like all sulphites, it releases active sulphur dioxide (E220) which prevents bacterial growth and stops food from turning brown.

How it is used in food

The standard sulphite for home and commercial wine.

Commonly found in

Wine and cider
Dried fruits
Processed potatoes

Health and safety

Asthma sensitivity and vitamin B1 destruction.

For most people E224 causes no problems at the levels found in food. But sulphites must be declared on labels in the EU, US and Australia/New Zealand, because for one group of people they are genuinely dangerous.

Severe asthma trigger

asthmatics and sensitive individuals · evidence: established

Sulphites can trigger bronchospasms, hives, and anaphylaxis in sensitive individuals (roughly 5-10% of asthmatics).

EFSA re-evaluation of sulfur dioxide and sulfites

Shares the family chemistry and allergen caution as E220.

Regulatory status

Region	Status	Notes
Australia & New Zealand FSANZ	Permitted	Permitted, mandatory allergen declaration.
European Union EFSA / European Commission	Permitted	Authorised for food use under EU regulations (Annex II).
United States FDA (Food and Drug Administration)	Permitted, must be declared on the label	GRAS, except in meats or fresh fruits/vegetables. Mandatory allergen declaration. “Contains sulfites”

Identification on labels

E-number: E224

Also printed asPotassium metabisulfite

Alternatives to this additive

E300: Ascorbic acid — Can prevent browning without triggering asthma.

How it is made

Produced by reacting sulphur dioxide gas with a solution of alkali carbonates or hydroxides.

Synthesis — Sulphur dioxide is absorbed in an aqueous alkaline solution.

Worth knowing

Famously known to winemakers as the "Campden tablet".

Conclusion

In roughly 5-10% of asthmatics, even trace amounts of sulphites can trigger bronchospasm, hives and, rarely, anaphylaxis — which is why they must be declared above 10 mg/kg. For everyone else the risk is far lower, though EFSA's 2016 re-evaluation described the safety data as inadequate, treated the 0.7 mg/kg ADI as provisional, and found high consumers exceeding it. Worth watching if you have asthma, worth not ignoring if you eat a lot of dried fruit and wine.

References

EFSA re-evaluation of sulfur dioxide and sulfites — EFSA

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Entry last reviewed 2026-07-28.

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