Sulfur dioxide and sulphites can trigger severe hypersensitivity reactions in humans. After eating foods containing sulfur affected people react with asthmatic conditions, hives (urticaria), gastro-intestinal discomfort up to anaphylactic symptoms. Asthma sufferers are particularly at risk in this type of adverse reaction, where even a tiny intake of sulfur for example, a glass of wine, can constrict the mucous membranes of the bronchial tubes.
Sulfur dioxide (SO2) and the salts of sulfurous acid, sulfites have been used as preservatives and anti-oxidants in the preparation of food for many centuries.
As an additive they are provided with E-numbers:
Sulfur dioxide and sulphite food must be labeled as an amount of 10 mg/l or 10 mg/kg in the list of ingredients or on the label. Watch out here for the term "sulfur" or the labeling "sulphurized”.