title: Damage to hair follicles by normal-mode ruby laser pulses.
abstract: BACKGROUND
  Although many temporary treatments exist for hirsutism and hypertrichosis, a practical and permanent hair removal treatment is needed.
  
  
  OBJECTIVE
  Our purpose was to study the use of normal-mode ruby laser pulses (694 nm, 270 microseconds, 6 mm beam diameter) for hair follicle destruction by selective photothermolysis.
  
  
  METHODS
  Histologically assessed damage in ex vivo black-haired dog skin after the use of different laser fluences was used to design a human study; 13 volunteers with brown or black hair were exposed to normal-mode ruby laser pulses at fluences of 30 to 60 J/cm2, delivered to both shaved and wax-epilated skin sites. An optical delivery device designed to maximize light delivery to the reticular dermis was used. Hair regrowth was assessed at 1, 3, and 6 months after exposure by counting terminal hairs.
  
  
  RESULTS
  Fluence-dependent selective thermal injury to follicles was observed histologically. There was a significant delay in hair growth in all subjects at all laser-treated sites compared with the unexposed shaven and epilated control sites. At 6 months, there was significant hair loss only in the areas shaved before treatment at the highest fluence. At 6 months, four subjects had less than 50% regrowth, two of whom showed no change between 3 and 6 months. Transient pigmentary changes were observed; there was no scarring.
  
  
  CONCLUSIONS
  Selective photothermolysis of hair follicles with the normal-mode ruby laser produces a growth delay consistent with induction of prolonged telogen with apparently permanent hair removal in some cases.
authors.affiliation: Wellman Laboratories of Photomedicine, Harvard Medical School, Massachusetts General Hospital, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Grossman
authors.forename: C
authors.initials: C
authors.lastname: Dierickx
authors.forename: W
authors.initials: W
authors.lastname: Farinelli
authors.forename: T
authors.initials: T
authors.lastname: Flotte
authors.forename: R R
authors.initials: RR
authors.lastname: Anderson
mesh_terms: D000818:Animals; D004285:Dogs; D005260:Female; D018859:Hair Follicle / Q000473:pathology* / Q000528:radiation effects; D006204:Hair Removal / Q000379:methods*; D006801:Humans; D007834:Lasers; D008297:Male; D012867:Skin / Q000473:pathology / Q000528:radiation effects