Lidocaine is used widely as an injectable local anesthetic, occasionally as an intravenous drug for cardiac arrhythmias, and increasingly as a topical anesthetic. Reports of allergic contact dermatitis and delayed hypersensitivity reactions to this "amide" anesthetic are limited. We report 16 cases of lidocaine contact allergy seen over 5 years. Concomitant patch-test reactions occurred with neomycin 20% (10 cases), bacitracin 20% (9 cases), fragrance mix 8% (3 cases), balsam of Peru 25% (2 cases), and dibucaine 2.5% and benzocaine 5% (1 case each). Patch tests with lidocaine dilutions (in petrolatum) gave the following results: 10% (3 of 4 positive reactions), 5% (4 of 6 positive reactions), and 1% (3 of 6 positive reactions). Intradermal testing with lidocaine 1%, mepivacaine 2%, and bupivacaine 0.5% was performed on 8 patients, resulting in positive reactions to lidocaine in 3 patients and to mepivacaine in 1 patient. Bupivacaine yielded negative results in each of the 8 patients. Relevance of delayed reactions to injectable lidocaine was definite in 2 cases; past, probable, and unknown in 1 case each; and possible in 11 cases. Delayed hypersensitivity to lidocaine may present as "suture allergy," treatment failure, typical contact allergy, or other local skin or dental reactions. Allergen substitution is based on further patch and intradermal testing, the results of which may be discordant.
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