The presence of substances known to induce pseudoallergic reactions was investigated by means of a questionnaire to the manufacturers of 1,467 frequently administered formulations. Benzoates were found in 15% of the formulations, sorbates in 5.5%, sulfites in 3.8%, and benzalkonium in 3.0%. The occurrence of the seven artificial colours studied was as follows: indigotin 7.8, erythrosine 7.4, sunset yellow 6.6, tartrazine 4.9, quinoline yellow 2.8%, ponceau (new coccine) 2.6, and amaranth 1.7%. A significant risk of exposure to preservatives and dyes likely to induce asthma, urticaria, or other pseudoallergic reactions exists for all individuals taking commercial drug products.