To the Editor.
—In the January issue of the Archives, Schwartz and Sher1 describe an asthmatic patient who experienced respiratory distress after being treated with an ophthalmic solution of dipivefrin hydrochloride containing 0.1% sodium metabisulfite.Sulfiting agent is a generic term used to describe any of a group of similar sulfur-containing chemicals employed as preservatives and antioxidants in the restaurant, fermentation, packaged food, and pharmaceutical industries. Six sulfiting agents have been listed by the Food and Drug Administration (FDA) as generally regarded as safe (GRAS) substances: sulfur dioxide, sodium sulfite, sodium and potassium bisulfite, and sodium and potassium metabisulfite. Under FDA regulation, labeling requirements for GRAS substances are not as inclusive as they are for other, more controlled substances.2 Currently, the GRAS status of these six agents is under review.Suspected adverse reactions to sulfiting agents have received increased attention in both the lay and medical literature. Those