Persistent urticaria is a rare side effect of laser epilation. Rupture of the hair follicle by laser heat may trigger a delayed hypersensitivity reaction in a subset of predisposed allergic patients. An antigen from the disrupted hair follicle may be the triggering factor. To prevent this side effect, we recommend that laser epilation in allergic patients be preceded by an extended laser patch test, which should be evaluated 24-48 hours later. Preventive prednisone should be prescribed to patients who develop an urticarial rash on the test area.