PHOTOALLERGY TO HEXAMIDINE

This report details the case of an atopic patient showing a photosensi tivity caused by a hexamidine solution. Patch tests were negative but photopatch tests to hexamidine in water solution were positive, after irradiation by ultraviolet A (UVA); all control tests were negative. I t is well-known that hexamidine can induce contact allergy but this ca se was the first reported in which UVA was implicated. This photoaller gy can be explained by the structure of the hexamidine molecule, but t he question is: why has there never been such a case reported before?