Persistent Reaction to Bacitracin after Patch Testing with Thin Layer Rapid Use Epicutaneous Test.

Long-lasting allergic patch test reactions (LLAPTR) are reactions that remain positive for two weeks or more after the application of the allergen. LLAPTR of longer than 6 weeks duration is rarely seen. Here we present a 54-year-old female patient who had a positive allergic reaction to bacitracin with the thin layer rapid use epicutaneous test (TRUE test), which lasted for about 11 weeks duration. To our knowledge this is the first reported case of LLAPTR related to the bacitracin.