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Damage to hair follicles by normal-mode ruby laser pulses
M C Grossman1, C Dierickx, W Farinelli
1Wellman Laboratories of Photomedicine, Harvard Medical School, Massachusetts General Hospital, USA.
Journal of the American Academy of Dermatology
|December 1, 1996
Summary
The normal-mode ruby laser effectively delays hair regrowth by targeting hair follicles. This selective photothermolysis offers a promising option for long-term hair removal, with some cases showing permanent results.
Area of Science:
- Dermatology
- Laser Physics
- Histopathology
Background:
- Existing hirsutism and hypertrichosis treatments are often temporary.
- A need exists for practical, permanent hair removal solutions.
Purpose of the Study:
- To investigate the efficacy of normal-mode ruby laser pulses for selective photothermolysis of hair follicles.
- To assess hair follicle destruction using specific laser parameters (694 nm, 270 µs, 6 mm beam diameter).
Main Methods:
- Histological assessment of ex vivo dog skin damage informed human study design.
- 13 volunteers with dark hair received ruby laser treatment (30-60 J/cm²) on shaved and epilated sites.
- Hair regrowth was monitored for 6 months post-treatment.
Main Results:
- Selective thermal injury to hair follicles was observed, dependent on laser fluence.
- Significant hair growth delay occurred at all treated sites compared to controls.
- Permanent hair reduction was noted in some subjects, particularly at higher fluences and shaved sites.
Conclusions:
- Normal-mode ruby laser selective photothermolysis induces prolonged telogen, delaying hair growth.
- This laser treatment shows potential for permanent hair removal in some individuals.
- Transient pigmentary changes were observed, but no scarring occurred.