Sulfites are sulfur-based compounds often used as preservatives in wines (to prevent spoilage and oxidation,) dried fruits, and dried potato products. About five percent of asthmatics have difficulty breathing within minutes of eating a food containing sulfites. People with allergies to aspirin are also at an elevated risk for reaction to sulfites. The reaction can be fatal and requires immediate treatment at an emergency room, and can include sneezing, swelling of the throat, and hives. (See also: anaphylaxis.) Sulfites occur naturally in almost all wines. Those bottled after mid-1987 must have a label stating that they contain sulfites if they have more than 10 parts per million of the additive. Organic wines are not necessarily sulfite-free, however most beers no longer contain sulfites. Although shrimp is sometimes treated with sulfites on fishing vessels, the chemical may not appear on the label. Those who are allergic to sulfites are urged to avoid products that could contain them. In 1985, the American federal government banned addition of sulfites to most fresh fruits and vegetables, though fresh-cut potatoes and dried fruits are exceptions.