title: Paradoxical hypertrichosis after laser epilation.
abstract: OBJECTIVE
  Hair removal using lasers or broadband intense pulsed light has become one of the most ubiquitous medical procedures. At our center a small proportion of patients have spontaneously reported what they believed to be increased hair growth at sites of previous laser epilation. We sought to retrospectively review the prevalence and features of this paradoxical effect.
  
  
  METHODS
  This was a single center, retrospective study that included all patients who underwent laser hair removal during a 4-year period with a long-pulsed alexandrite laser. All cases of laser-induced hypertrichosis were assessed clinically by history, examination, and laboratory tests, and confirmed by review of serial clinical photographs taken during the course of the laser treatments. The clinical features of patients with postlaser hypertrichosis were compared with 50 patients randomly selected from among all those who had undergone laser hair removal at our center (n = 489).
  
  
  RESULTS
  Of 489 patients, 3 (0.6%, 95% confidence interval: 0.01-1.9%) treated with the long-pulsed alexandrite laser (755 nm) reported increased hair after laser hair epilation. There was a trend for this adverse effect to occur in darker skin phototypes (IV) and with black hair as compared with the unaffected comparison group (n = 50). However, the small number of cases (n = 3) did not provide sufficient power to adequately test factors such as age, sex, treatment settings, and number of treatments statistically.
  
  
  CONCLUSIONS
  Postlaser hair removal hypertrichosis is a real but rare occurrence in our experience.
authors.affiliation: Division of Dermatology, Vancouver Coastal Health Research Institute, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Abdulmajeed
authors.initials: A
authors.lastname: Alajlan
authors.forename: Jerry
authors.initials: J
authors.lastname: Shapiro
authors.forename: Jason K
authors.initials: JK
authors.lastname: Rivers
authors.forename: Nina
authors.initials: N
authors.lastname: MacDonald
authors.forename: Judy
authors.initials: J
authors.lastname: Wiggin
authors.forename: Harvey
authors.initials: H
authors.lastname: Lui
mesh_terms: D000328:Adult; D005260:Female; D006204:Hair Removal / Q000009:adverse effects*; D006801:Humans; D006983:Hypertrichosis / Q000453:epidemiology / Q000209:etiology*; D007834:Lasers / Q000009:adverse effects*; D008297:Male; D012189:Retrospective Studies