Sulfites or sulphites are compounds that contain the sulfite ion, SO2− 3, which is the conjugate base of bisulfite. Although its acid (sulfurous acid) is elusive, its salts are widely used. Sulfites are substances that naturally occur in some foods and the human body, and they are also used as regulated food additives. Sulfites release sulfur dioxide gas, which is the active component that helps preserve drinks, foods, and medications. Sulfites are used as preservatives to slow browning and discoloration in foods and beverages during preparation, storage, and distribution. Some common sources of sulfites include dried fruit, potato chips, trail mix, beer, wine, and many condiments. Sulfites can trigger asthma and symptoms of an anaphylactic reaction, and many people who have asthma may also have a sulfite sensitivity. If you have a sulfite sensitivity, it’s important to check food labels for sulfites so you can avoid a reaction. In Canada, sulfites must be listed on the package label, and Canadian guidelines require that sulfite-containing products are clearly labeled.