[Clinical study of patients with positive reactions in patch tests with local anesthetics]

Local anesthetics have been contained in various OTC drugs and the number of cases of allergic contact dermatitis due to local anesthetics has increased recently. Thirty-five hundreds and fourteen cases suspected of suffering from drug eruption or contact dermatitis were the subjects of this study during the 8 years from January, 1988 to December, 1995. One hundred and thirty-eight cases, suspected of having allergic contact dermatitis were patch tested with topical medicaments including local anesthetics and 70 (50.7%) of them showed positive. In 49 of the 60 cases who reacted positively to anesthetics extensive patch tests with the individual ingredients of the products were carried out. The local anesthetics causing positive reactions were as follows (in order of frequency): dibucaine hydrochloride (35 cases: 71.4%), ethyl aminobenzoate (12 cases: 24.5%), lidocaine hydrochloride (2 cases: 4.1%), and procaine hydrochloride (1 case: 2.0%). The number of patients displaying allergies to local anesthetics has increased, especially cases caused by dibucaine hydrochloride. And the total positive reaction rate to dibucaine hydrochloride in the patch tests was 3.7%, which was as high that to the well-known strong sensitizer PPDA (3.9%) and neomycin (2.9%). Forty-three cases sensitive to local anesthetics were also studied for cross-sensitivity.