E222 (sodium hydrosulfite, sodium hydrosulfite)

E222 is sodium bisulfite, also called sodium hydrogen sulfite, one of the additives in the sulfur dioxide and sulfite group. In foods it is used as a preservative and antioxidant: it helps slow oxidation, browning, flavor changes, and the growth of some microorganisms. It is a technological salt, not a dietary sodium supplement and not a useful sulfur source. Its practical meaning is always connected with product stability.

How bisulfite differs from sulfite

E221 is sodium sulfite, while E222 is sodium bisulfite, a more acidic form within the same sulfite chemistry. In food, these forms may be connected with pH, solubility, oxidation reactions, and release of sulfur dioxide. For a technologist, this difference matters because different salts fit different formulas. For the consumer, the key point is that E222 belongs to the sulfite group and may raise the same practical tolerance questions as other E220-E228 additives.

The word sodium again does not mean the additive should be seen as an electrolyte. Sodium can indeed matter in a keto diet, especially during adaptation, fluid loss, or low blood pressure. But it is obtained from salt, broth, mineral water, or electrolyte formulas. Sodium bisulfite is used not to support electrolytes but to protect the food from spoilage and oxidation.

Where E222 may appear

Sodium bisulfite may be used in certain fruit and wine-related products, processed vegetables, preserved foods, marinades, sauces, dried fruit, and other products where stability is needed. Specific use depends on the country and food category rules. In home cooking, the role is usually replaced by understandable methods: refrigeration, freshness, salt, acidity, fermentation, heat treatment, clean containers, and short storage.

From a low-carb perspective, E222 does not add sugar. But a product containing it may be dry wine with little sugar, dried fruit with high carbohydrate density, or a sweet fruit preparation. Keto assessment therefore begins not with the sulfite but with sugar, starch, syrups, fruit content, portion size, and frequency of use. Only after that should sulfites be considered as a tolerance factor.

Sensitivity and real reactions

Sulfite sensitivity does not affect everyone, but for a susceptible person it can be very noticeable. Reactions may involve the airways, skin, head, and gastrointestinal tract: coughing, wheezing, stuffiness, headache, flushing, itching, nausea, or mucous membrane irritation. People with asthma are usually the group advised to pay particular attention. If symptoms repeat after wine, dried fruit, or foods labeled as containing sulfites, E222 and related additives should be considered.

At the same time, everything should not be reduced to one substance. Wine contains alcohol and may contain biogenic amines. Dried fruit delivers a large dose of sugars. Marinades and sauces may be acidic, salty, spicy, or contain sweeteners. When a reaction occurs, it is more useful to look at repetition: which products, which portions, which symptoms, and how quickly they appear. Such a diary can reveal the real connection.

Practical conclusion

EFSA considers E222 together with other sulfites because safety depends on total exposure to this group. In everyday eating, the main question is not whether E222 breaks keto; it is not a carbohydrate. The question is what product contains it and how the person tolerates the sulfite group. Dried fruit is usually limited because of sugar, wine because of alcohol and individual response, and sauces because of the whole formula.

If the base of the diet is simple and fresh, E222 will be a rare label line. If a person often consumes wine, dried fruit, industrial marinades, and preserved foods, sulfite exposure may add up. With asthma, repeated headaches, skin reactions, or irritation after such products, it is reasonable to reduce frequency, compare with sulfite-free alternatives, and discuss persistent symptoms with a clinician.