Evaluation of intolerance to analgesics, preservatives and food colorants with challenge tests

In 504 patients with asthma or rhinitis 1,868 oral challenge tests with analgesics, preservatives and food colorants were performed. Sodium benzoate and other benzoic compounds, as well as tartrazine and other azo dyes, were found to give similar but milder adverse reactions than acetylsalicylic acid. No patients reacted to potassium sorbate, another preservative, or to Patent Blue, which is not an azo dye. Intolerance was demonstrated most frequently in patients with a history of adverse reactions to analgesics or food, but also in 6% of patients investigated for other reasons. There are obvious risks for false positive or false negative results with a challenge test. Examples of these are given. The need for repeated tests and the clinical importance of all reproducible challenge reactions is stressed.