Pulmonary reactions to sulfites in foods

Sulfites or sulfiting agents include sulfur dioxide (SO 2 ) and a number of inorganic salts (including sodium and potassium metabisulfite, Na 2 S 2 O 5 , K 2 S 2 O 5 ), sodium and potassium bisulfite (NaHSO 3 , KHSO 3 ) and sodium sulfite (Na 2 SO 3 ), which liberate sulfur dioxide under the conditions of use. Isolated reports of sulfite sensitivity appeared in the medical literature during the mid to late 1970s, but it was not until 1981 with the report of Stevenson & Simon (6) that the problem began to become widely recognized. Since that report, a number of investigators worldwide have demonstrated that approximately 5% of asthmatics react to sulfites placed in acidic solutions at levels comparable to that previously found in food, utilizing double‐blind, placebo‐controlled studies. Sulfite addition to foods served a number of purposes, including inhibition of enzymatic browning, the inhibition of non‐enzymatic browning, antimicrobial actions, dough conditioning effects, antioxidant purposes, bleaching applications, and others. Foods that contained significant amounts of sulfite included fresh fruits and vegetables (salads), guacamole, shrimp, potatoes, dehydrated vegetables, dried fruits, wine, citrus drinks, juices, vinegar, and pickled foods. In 1985 the Food and Drug Administration required the declaration of sulfites on the labels of foods with sulfite residues exceeding 10 ppm SO 2 , and the Bureau of Alcohol, Tobacco and Firearms followed suit with wines. In 1986 the FDA banned the use of sulfites from fresh fruits and vegetables other than potatoes. This ban particularly affected the once common practice of sulfiting the fresh fruits and vegetables in salad bars. Most recently the FDA has banned sulfites from fresh, pre‐peeled potatoes. These actions have helped protect sulfite‐sensitive individuals from the hazards associated with sulfited foods. However, since sulfites are still used in many foods (and drugs), sensitive individuals must be cautious to avoid inadvertent exposure. There are a number of proposed mechanisms for pulmonary reactions to sulfites. Clearly, the overwhelming majority of asthmatic reactions result from the inhalation of sulfur dioxide liberated under conditions of use. Asthmatic airways are particularly sensitive to the effects of sulfur dioxide, probably by stimulation of irritant/cholinergic receptors. Other possible mechanisms, particularly associated with ingestion of foods containing sulfites in bound form, are sulfite oxidase deficiency and also implicated in anaphylactic reactions, IgE‐mediated mechanisms. Reactions provoked as a result of these latter two mechanisms represent a very small percentage of adverse reactions to sulfites.