title: The role of natural and UV-induced skin pigmentation on low-fluence IPL-induced side effects: a randomized controlled trial.
abstract: OBJECTIVE
  The risk of adverse skin effects following light-based hair removal is greater in pigmented skin based on the theory of selective photothermolysis. Thus sunlight-induced pigment i.e., facultative pigmentation, increases the risk of adverse skin effects, perhaps disproportionately. The aim of this study was to evaluate the influence of constitutive and facultative skin pigmentation on low-fluence intense pulsed light (IPL)-induced adverse skin effects.
  
  
  METHODS
  Twenty-one subjects with Fitzpatrick skin type II-IV were enrolled. Two buttock blocks were randomized to receive 0 or 8 solar simulated ultraviolet radiation (UVR) exposures of consecutively increasing Standard Erythema Doses (2-4 SED). Each block was subdivided into four sites, randomized to receive IPL of 0, 7, 8, or 10 J/cm(2) , once a week for 3 weeks. Biopsies were taken 16-24 hours after the first IPL exposure and subjects were seen 1 and 4 weeks after the last IPL exposure. Outcome measures were: (i) skin reactions, (ii) pain, (iii) mRNA expression of pigment-markers microphthalmia-associated transcription factor (MITF) and pro-opiomelanocortin (POMC), and (iv) clinical appearance of biopsy wounds.
  
  
  RESULTS
  Skin pigmentation increased after UVR (baseline median 13.8%, after UVR 28.1%, P = 0.0001) in all skin types. Subjects reported low pain intensities (median 1.5, scale 0-10) and experienced transient erythema immediately after IPL exposure. No persistent erythema, blisters, crusting, textual, or pigment changes were observed. The risk of erythema and pain intensities increased with IPL dose and skin pigmentation (P < 0.03). There was no difference in pain or skin reactions in skin with similar degree of natural and facultative pigmentation (P ≥ 0.104). Expression of cellular pigment-markers was not influenced by IPL exposure, neither in constitutive nor in facultative pigmented skin. Clinical appearance of biopsy wounds was unaffected by IPL exposure.
  
  
  CONCLUSIONS
  The prevalence and intensity of low-fluence IPL-induced adverse skin effects depended on IPL dose and skin pigmentation regardless of the origin, i.e., constitutive versus UV induced.
authors.affiliation: Department of Dermatology, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Daniel
authors.initials: D
authors.lastname: Thaysen-Petersen
authors.forename: Jennifer Y
authors.initials: JY
authors.lastname: Lin
authors.forename: Jf
authors.initials: J
authors.lastname: Nash
authors.forename: Frank
authors.initials: F
authors.lastname: Beerwerth
authors.forename: Hans C
authors.initials: HC
authors.lastname: Wulf
authors.forename: Peter A
authors.initials: PA
authors.lastname: Philipsen
authors.forename: Merete
authors.initials: M
authors.lastname: Haedersdal
mesh_terms: D000328:Adult; D001768:Blister / Q000209:etiology; D004890:Erythema / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007834:Lasers / Q000009:adverse effects*; D008297:Male; D010146:Pain / Q000209:etiology; D012867:Skin / Q000528:radiation effects*; D012880:Skin Pigmentation; D055107:Suntan; D014466:Ultraviolet Rays / Q000009:adverse effects*
keywords: UV exposure; adverse events; hair removal; home-use device; microphthalmia-associated transcription factor; proopiomelanocortin; skin type; tanning