The salts of sulfurous acid, which may be used in food processing for any of various reasons, including the deterrence of insects and diseases, inhibiting bacterial growth and preventing spoilage or oxidation. Sulfites, which may be added as a preservative to packaged and processed foods, can cause severe allergic reactions (such as hives, shortness of breath and even anaphylactic shock) in certain individuals. For that reason, in 1986 the Food and Drug Administration prohibited their use on "fresh fruits and vegetables intended to be sold or served raw to consumers." In the United States, the words "Contains Sulfites" (or similar verbiage) are mandatory on labels of foods that include sulfites.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.