Benzocaine--an unsatisfactory indicator of topical local anaesthetic sensitization for the U.K.

Three thousand consecutive patients undergoing patch tests were tested with a mix of benzocaine, amethocaine hydrochloride and cinchocaine hydrochloride. Eighty-four subjects (2.8%) were found to be allergic to this mix. Forty of these were patch tested with the constituents of the mix: 21 (52.5%) patients were sensitive to amethocaine hydrochloride or cinchocaine hydrochloride or both, but not to benzocaine. We recommend that a non-irritant 'caine mix' containing benzocaine, cinchocaine and amethocaine should be included in the standard patch test series for the U.K.