Urticaria induced by laser epilation: a clinical and histopathological study with extended follow-up in 36 patients.

Background: Laser epilation is the most common dermatologic light-based procedure in the world. We describe a unique side effect of the procedure: a delayed persistent urticarial rash.

Patients And Methods: We conducted a retrospective study involving 13,284 patients who received laser epilation at our clinics from January 2006 through March 2010 with 755 nm alexandrite laser (MiniGentleLase, Gentlelase, and GentleMax, Candela). Using patient clinical data and photos that were recorded on a standard side-effect report chart, we identified patients with suspected urticaria. Those patients were then followed for a period that ranged from 12 to 63 months. Only patients who could be diagnosed, treated, and followed by the dermatologist at our clinics were included in the study. Patients diagnosed or treated by other physicians or nurses and those without clinical photos or insufficient follow-up data were not included.

Results: We identified 36 patients who developed a severe, itchy, persistent hive rash on the treated area 6-72 hours after treatment. Eruption occurred most often on the legs (31 cases), followed by the groin (11 cases), axillae (eight cases), forearms (one case), and upper lip (one case). The eruption consisted of a hive rash with multiple pruritic perifollicular papules and confluent plaques on the treated area. Most patients required oral corticosteroids to control the symptoms. Lesions resolved in 7-30 days. The urticaria occurred mostly after the first treatment (26 cases), and was recurrent in subsequent treatments. Pretreating with oral corticosteroids prevented or limited the eruption. Thirty-three of the 36 patients reported a history of allergic rhinitis or some other allergy. Skin biopsies on four patients showed edema and a deep, dense dermal infiltrate consistent with lymphocytes mixed with eosinophils in a perivascular and occasionally perifollicular pattern in the mid and lower dermis.

Conclusions: 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.