Allergic contact dermatitis from pimecrolimus in a patient with tacrolimus allergy

A 15-year-old male with previously documented allergic contact dermatitis from tacrolimus was allergic to pimecrolimus. This was demonstrated by double-blinded, right-versus-left provocative use testing with pimecrolimus cream 1% versus inactive vehicle applied twice daily to normal skin. The active cream but not its vehicle caused preauricular dermatitis starting after 1 week and caused isolated papules on the extensor wrist starting after 2 weeks. Patch testing on the patient's back was weakly positive (1+) with pimecrolimus cream 1% and negative with the vehicle. Higher concentrations of pimecrolimus were not available for testing. Patch tests on 30 control patients with pimecrolimus cream 1% were negative.