Grossman, 1996 (ruby hair removal dog test)

Grossman, 1996

Title: Damage to hair follicles by normal-mode ruby laser pulses.

Authors: Grossman MC, Dierickx C, Farinelli W, Flotte T, Anderson RR

Journal: J Am Acad Dermatol 1996 Dec;35(6):889-94

PMID: 8959946, UI: 97119123

Affiliated institution: Wellman Laboratories of Photomedicine, Harvard Medical School, Massachusetts General Hospital, USA.

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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.

CONCLUSION: 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.

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