Forty-five patients with moderately severe perennial bronchial asthma were challenged by ingestion of: acetylsalicyclic acid (ASA); 4 azo dyes (tartrazine, sunset yellow, amaranth, and ponceau); 3 non-azo dyes (erythrosine, brilliant blue, and indigotin); sodium benzoate (NaB); parahydroxybenzoic