LAUSR

Patch tests with drugs are essential for the diagnosis of cutaneous adverse drug reactions (CADRs), especially in severe reactions. It is recommended to perform skin tests within 4 to 6 weeks to several months (particularly for drug rash with eosinophilia and systemic syndrome [DRESS]) after complete resolution of the drug eruption. Nevertheless, there is little evidence concerning the maximum period during which tests are feasible, and tests are not usually performed beyond an interval of 1 year. We report a positive drug patch test reaction almost 20 years after the CADR, and we discuss testing patients after a very long delay following the CADR.