Title: Histological study of hair follicles treated with a 3-msec pulsed ruby laser.
Authors: McCoy S, Evans A, James C
Journal: Lasers Surg Med 1999;24(2):142-50
PMID: 10100652, UI: 99198751
Affiliated institution: The Laser, Skin and Vein Clinic, North Adelaide, South Australia, Australia. firstname.lastname@example.org
BACKGROUND AND OBJECTIVE: Ruby laser energy at 694 mn is moderately absorbed by melanin and minimally absorbed by other skin chromophores. This property and its depth of penetration into dermis permit absorption into pigmented hair follicles, thus making it suited to photothermolysis of these appendages. Clinical reports of the efficacy of such lasers for removal of unwanted hair are emerging in large numbers, but scientific data regarding the exact mechanism of action is still lacking. This study aims to evaluate and define further the histological responses of hair follicles to 3-msec pulsed ruby laser light.
STUDY DESIGN/MATERIALS AND METHODS: Twenty-four patients with brown or black axillary or groin hair were treated with a 3-msec ruby laser at fluences from 10 to 40 J/cm2 on one, two, or three occasions. Biopsies were taken at various intervals from immediately to 8 weeks after treatments. Biopsies were fixed and stained with either nitroblue tetrazolium chloride or hematoxylin and eosin for histological examination.
RESULTS: One treatment induced changes typical of catagen followed by telogen at all fluences. The papillae always remained viable. Two and three treatments resulted in atypical telogen, with infundibular dilatation and plugging, and marked proliferation of the stem outer sheath. New anagen follicles were evident even after three treatments at 12- and then 8-week intervals and were biopsied 6 weeks later, but there were no hairs extending to or through the epidermis.
CONCLUSION: There was no evidence of permanent follicle death after one ruby laser treatment. However, despite evidence of persistence of follicular elements after two and three treatments, it is possible that laser-induced damage to the isthmus and upper stem may interfere with the interaction between dermal and epidermal germinative cells, thus inhibiting or altering the normal hair cycle.
1. Grossman MC, Dierickx C, Farinelli W, Flotte T, Anderson RR. Damage to the hair follicles by normal-mode ruby laser pulses. J Am Acad Dermatol 1996;35:889-95
2. Proceedings of the 18th Annual Meeting of the American Society for Laser Medicine and Surgery. Lasers Surg Med 1998 Suppl. 10 Anstr 186-191, 198-201, 203, 205, 206.
3. Gold MH, Bell MW, Foster TD, Street S. Long-term epilation using the EpiLight broad band, intense pulsed light hair removal system. Dermatol Surg 1997;23:737-739
4. Goldberg DJ, Littler CM, Wheeland RG. Topical suspension-assisted Q-switched Nd:YAG laser hair removal. Dermatol Surg 1997 Sep;23(9):741-5
5. Lask G, Elman M, Slatkine M, Waldman A, Rozenberg Z. Laser-assisted hair removal by selective photothermolysis. Preliminary results. Dermatol Surg 1997 Sep;23(9):737-9
6. Proceedings of the First Intercontinental Meeting of Hair Research Societies. Aus J Dermatol 1997;38(4):A320-A321.
7. Wheeland RG. Laser-assisted hair removal. Dermatol Clin 1997;15:469-477
8. Hynd PI, Hughes A, Earl CR, Penno NM. Seasonal changes in the morphology of wool follicles in Finewool and Strongwool Merino strains grazing at different stocking rates in Southern Australia. Aust J Agricul es 1997;48:1089-1097
9. Saitoh M, Uzuka M, Sakamoto M. Human hair cycle. J Invest Dermatol 1970 Jan;54(1):65-81
10. Jahoda CA, Reynold AJ. Dermal-epidermal interactions. Adult follicle-derived cell populations and hair growth. Dermatol Clin. 1996 Oct;14(4):573-83.
11. Kim JC, Choi YC. Regrowth of grafted human scalp hair after removal of the bulb. Dermatol Surg 1995;21:312-313