context: Sulfites are a common additive in many foods and drugs. Sulfites also occur naturally in some foods. Unfortunately, 5%-10% of people with asthma are also allergic to sulfites. An allergy is an increased sensitivity to a specific substance (called an allergen). The combination of asthma and sulfites can be dangerous. If you have asthma and sulfite allergy, eating foods or taking drugs that contain sulfites can even be life-threatening. " Sulfites" is the general name for six specific substances: Sulfur dioxide Sodium sulfite Sodium bisulfite Sodium metabisulfite Potassium bisulfite Potassium metabisulfite As additives, sulfites do many things: They can prevent spoilage and preserve foods -- and certain beverages -- by preventing the growth of mold and bacteria, for example. They can stop fruits, vegetables, and seafood from discoloring. They can maintain the strength of common medications -- including some asthma drugs. Sulfites may be added to foods and beverages such as: Apple cider and other types of cider Avocado dip Beer and wine Condiments, jams, gravies, and molasses Dried fruits and vegetables Fruit and vegetable juices Peeled potatoes (including french fries) Pickled meats and vegetables Restaurant food and other prepared foods Shrimp and shellfish Sulfites may also occur naturally in foods such as: Asparagus Chives Corn starch Eggs Fish, such as salmon and dried cod Garlic Leeks Lettuce Maple syrup Onions Soy Tomatoes According to federal law, sulfites cannot be added to foods that are intended to be eaten raw, such as fruits and vegetables. When they are used as a preservative in food preparation or processing, they must be listed as an ingredient. The severity of allergic reactions to sulfites can vary. Symptoms of a sulfite allergy include: Hives and itchiness Upset stomach, diarrhea, and vomiting Trouble swallowing Flushing Dizziness Drop in blood pressure Trouble breathing The combination of asthma and sulfites can be life-threatening because it can lead to anaphylactic shock. If this occurs, the entire body reacts severely to the allergen. The airways can swell shut, making it difficult to breathe. According to the American Academy of Asthma, Allergy and Immunology, as many as 5%-10% of sulfite reactions in people with asthma are fatal. If you have signs of an allergic reaction to sulfites, get emergency help. In many cases, using your quick-relief inhaler can help control your reaction. If you have an epinephrine injection kit available, use it without hesitation, even if those symptoms do not appear to be allergy related. Using the pen as a precaution will not harm you and could save your life. Call 911 even after injecting yourself. Your doctor can tell if you have a sulfite allergy with a test called a controlled sulfite challenge. During this test, you are exposed to a small amount of sulfites under close supervision to see if you have a reaction. If you have asthma -- and sulfites cause an allergic reaction -- you need to be very careful to avoid them. This can be tough, especially since sulfites are in many foods and drugs. And even a very small amount can cause a reaction. But here are a few things you can do. Read labels, checking for sulfite substances listed above. Be careful with foods that commonly contain sulfites. Many are listed above. When you eat out, ask the waiter or waitress whether the food you're ordering contains sulfites. Check with your doctor to make sure that the asthma drugs you use do not contain sulfites. Be prepared in case you do ever accidentally eat sulfites. Ask your doctor what to do in an emergency. Always carry your rescue inhaler and an epi-pen with you.