Sulphites or sulfites are compounds that contain the sulfite ion, SO2− 3, which is the conjugate base of bisulfite. They are used as a food additive and can also occur naturally in some foods. Sulphites are used as preservatives to maintain food color, shelf-life, and prevent discoloration. They are also used in the pharmaceutical industry as preservatives and antioxidants. Sulphites are found in a variety of foods and drinks, including baked goods, canned/frozen fruits and vegetables, wine, beer, cider, and bottled lemon and lime juice/concentrate. They can also be found in cosmetics, perfumes, and many medicines. Sulphites can cause allergic-like symptoms in some individuals, and Health Canada includes sulphites as a priority allergen. Sulphite-sensitive individuals may react to sulphites with allergy-like symptoms, including asthma and symptoms of an anaphylactic reaction. However, sulphites are safe for most people, and a sulphite sensitivity is not a true allergy. Canadian guidelines require that sulphite-containing products are clearly labeled, and the ingredient list will say “contains: sulphites” if it contains this ingredient. It may also say “May contain sulphites” if there is a chance the product has come into contact with sulphites. Some other names for sulphites include potassium bisulphite, potassium metabisulphite, sodium bisulphite, sodium dithionite, sodium metabisulphite, disodium sulphite, sulfite, sulfur dioxide, sulphiting agents, sulphurous acid, E 220, E 221, E 222, E 223, E 224, E 225, E226, E227, E 228 (European names).