Sulfite-treated lettuce challenges in sulfite-sensitive subjects with asthma.

This study was designed to determine whether lettuce treated with a commercially available sulfite-containing freshener prepared according to manufacturer's directions could provoke reactions in sulfite-sensitive subjects with asthma (SSAs). Five adult SSAs with stable asthma who had multiple prior reactions to double-blind, placebo-controlled, sulfite-capsule challenges were studied. Each patient ingested, in a double-blind, placebo-controlled fashion, four portions of lettuce (3 oz) pretreated with one of two commercially available, nearly identical vegetable fresheners. One freshener contained sodium bisulfite and was used on one portion of lettuce. The other freshener contained no sulfite and was used on three portions of lettuce. The fresheners were prepared and the lettuce was treated according to label instructions. After baseline spirometry, the SSAs consumed the lettuce samples with the same dressing of their choice, serial spirometry was performed, and a positive reaction was defined as a greater than 20% drop in FEV1 decreased 0% to 7%; mean, 3%. Two of the subjects experienced severe reactions to the sulfite-treated lettuce. One of these reactions was life threatening; the other reaction occurred despite placing only 30% of the usual sulfite dose on the lettuce. This study has demonstrated that sulfite-treated lettuce is capable of provoking bronchospasm in SSAs and suggests that such food is one cause of restaurant-provoked asthma in these individuals.