Dermographic urticaria induced by long-pulsed diode laser-assisted epilation: Rare etiology of a common eruption

This document reported a rare case of dermographic urticaria induced by an 810 nm long-pulsed diode laser used for hair removal in a 36-year-old woman. The patient developed linear, erythematous, mildly itchy wheals shortly after laser treatment, which subsided spontaneously within 2 hours. She had a history of chronic episodic urticaria but was lesion-free for 2 months before the laser treatment. The urticaria recurred after subsequent laser sessions but was prevented by taking levocetirizine prophylactically. The exact cause of urticaria following laser epilation was unknown, but it was suggested that the laser might have triggered local mast cell degranulation. The patient remained free from urticaria 6 months after the last laser session.