Of all the food additives for which FDA has received adverse reaction reports, the ones that most closely resemble true allergens are sulfur-based preservatives. Sulfites are used primarily as antioxidants to prevent or reduce discoloration of light-colored fruits and vegetables, such as dried apples and potatoes, and to inhibit the growth of microorganisms in fermented foods such as wine. Though most people don't have a problem with sulfites, they are a hazard of unpredictable severity to people, particularly asthmatics, who are sensitive to these substances.
Responses range from mild to life-threatening.
FDA's sulfite specialists say scientists, at this time, are not sure how the body reacts to sulfites. To help sulfite-sensitive people avoid problems, FDA requires the presence of sulfites in processed foods to be declared on the label, and prohibits the use of sulfites on fresh produce intended to be sold or served raw to consumers.