McCoy, 1999  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.
suemccoy@senet.com.au
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.
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