title: Quantitative assessment of growing hair counts, thickness and colour during and after treatments with a low-fluence, home-device laser: a randomized controlled trial.
abstract: BACKGROUND
  At-home laser and intense pulsed-light hair removal continues to grow in popularity and availability. A relatively limited body of evidence is available on the course of hair growth during and after low-fluence laser usage.
  
  
  OBJECTIVE
  To assess growing hair counts, thickness and colour quantitatively during and after cessation of low-fluence laser treatment.
  
  
  METHODS
  Thirty-six women with skin phototypes I-IV and light to dark-brown axillary hairs were included. Entire axillary regions were randomized to zero or eight self-administered weekly treatments with an 810-nm home-use laser at 5·0-6·4 J cm(-2). Standardized clinical photographs were taken before each treatment and up to 3 months after the final treatment for computer-aided quantification of growing hair counts, thickness and colour.
  
  
  RESULTS
  Thirty-two women completed the study protocol. During sustained treatment, there was a reduction in growing hair that reached a plateau of up to 59%, while remaining hairs became up to 38% thinner and 5% lighter (P < 0·001). The majority of subjects (77%) reported 'moderately' to 'much less hair' in treated than untreated axilla, and assessed remaining hairs as thinner and lighter (≥ 60%). After treatment cessation, hair growth gradually returned to baseline levels, and 3 months after the final treatment the count and thickness of actively growing hair exceeded pretreatment values by 29% and 7%, respectively (P ≤ 0·04).
  
  
  CONCLUSIONS
  Sustained usage of low-fluence laser induced a stable reduction of growing hair counts, thickness and colour. The reduction was reversible and hairs regrew beyond baseline values after cessation of usage. Computer-aided image analysis was qualified for quantification of hair counts, thickness and colour after laser epilation.
authors.affiliation: Department of Dermatology, Bispebjerg Hospital, University of Copenhagen, Bispebjerg Bakke 23, DK-2400, Copenhagen NV, Denmark.
authors.forename: D
authors.initials: D
authors.lastname: Thaysen-Petersen
authors.forename: M
authors.initials: M
authors.lastname: Barbet-Pfeilsticker
authors.forename: F
authors.initials: F
authors.lastname: Beerwerth
authors.forename: J F
authors.initials: JF
authors.lastname: Nash
authors.forename: P A
authors.initials: PA
authors.lastname: Philipsen
authors.forename: P
authors.initials: P
authors.lastname: Staubach
authors.forename: M
authors.initials: M
authors.lastname: Haedersdal
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006197:Hair / Q000254:growth & development*; D006200:Hair Color; D006204:Hair Removal / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D053685:Laser Therapy / Q000009:adverse effects / Q000295:instrumentation*; D008875:Middle Aged; D010781:Photography; D012648:Self Care; D016896:Treatment Outcome; D055815:Young Adult