Title: Permanent hair removal by normal-mode ruby laser.
Authors: Dierickx CC, Grossman MC, Farinelli WA, Anderson RR
Journal: Arch Dermatol 1998 Jul;134(7):837-42
PMID: 9681347, UI: 98344672
Affiliated institution: Wellman Laboratories of Photomedicine, Harvard Medical School, Boston, Mass 02114, USA.
Full text is available at the Archives of Dermatology website
Objective: To assess the permanence of hair removal by normal-mode ruby laser treatment.
Methods: Hair removal was measured for 2 years after a single treatment with normal-mode ruby laser pulses (694 nm, 270 microseconds, 6-mm beam diameter).
Observations: Six test areas on the thighs or backs of 13 volunteers were exposed to normal-mode ruby laser pulses at fluences of 30 to 60 J/cm2 delivered to both shaved and wax-epilated skin. In addition, there was a shaved and wax-epilated control site. Terminal hairs were manually counted before and after laser exposure. Transient alopecia occurred in all 13 participants after laser exposure, consistent with induction of telogen. Two years after laser exposure, 4 participants still had obvious, significant hair loss at all laser-treated sites compared with the unexposed shaved and wax-epilated control sites. In all 4 participants, there was no significant change in hair counts 6 months, 1 year, and 2 years after laser exposure. Laser-induced alopecia correlated histologically with miniaturized, velluslike hair follicles. No scarring and no permanent pigmentary changes were observed.
Conclusions: Permanent, nonscarring alopecia can be induced by a single treatment with high-fluence ruby laser pulses. Miniaturization of the terminal hair follicles seems to account for this response.
UNWANTED HAIR is a major cosmetic and surgical problem. Many temporary hair removal methods exist, including shaving, wax epilation, and use of chemical depilatories.[1,2] Electrolysis is a well-established method for permanent destruction of terminal hair follicles. However, the method is tedious, and efficacy has been reported to range from 15% to 50% permanent hair loss. Scarring can occur after electrolysis, especially if inexpertly performed.
Damage to hair follicles based on the theory of selective photothermolysis has been reported recently. Thirteen volunteers with brown or black hair were exposed to normal-mode ruby laser pulses (694 nm, 270 microseconds, 6-mm beam diameter) at fluences of 30 to 60 J/cm2 delivered to both shaved and wax-epilated skin sites on the thighs or back. In all 13 participants, laser exposures produced a hair growth delay consistent with induction of telogen. Ruby lasers have been commercialized for hair removal, but the question remains whether permanent hair loss can be induced by selective photothermolysis. Four study participants had clinically obvious hair loss at the final follow-up visit 6 months after exposure, each of these with less than 50% regrowth of terminal hairs. We decided to follow up the participants of this first study at 1 and 2 years after laser exposure to evaluate the permanence of hair removal.
PARTICIPANTS AND METHODS
Thirteen adult volunteers (12 men and 1 woman) consented to participate, as previously described. All had fair skin (Fitzpatrick type I, II, or III) and brown or black hair. Test sites were chosen on the back or posterior aspect of the thighs based on uniformity and density of terminal hairs. Eight 3×2-cm areas were mapped and photographed. Baseline hair counts were obtained from each site by manually counting and marking terminal hairs. Before laser exposure, half of the test sites were shaved and half were epilated with cold wax (My-Epil, Laboratoire Suzy, Montreuil, France). Sites were irradiated with a normal-mode ruby laser, described below, at fluences of 0 (unexposed control), 30, 40, and 60 J/cm2. Laser pulses were given in a contiguous, nominally nonoverlapping pattern that covered the entire test site.
Clinical evaluation, terminal hair counts, and photographs were obtained 1, 3, 6, 12, and 24 months after laser exposure. One participant who had obvious alopecia in all laser exposure sites at all of these follow-up visits consented to biopsy examination. Three-millimeter punch biopsy samples were obtained before treatment and at 1 year after laser exposure from a site with alopecia treated at 60 J/cm2 after shaving. Tissue specimens were processed for light microscopy of horizontal sections with a technique using trisection or quadrisection that maintains all sections in the same anatomic orientation (deep to superficial) on the microscope slides. All specimens were stained with hematoxylin-eosin for light microscopy.
Hair loss was defined as the percentage of terminal hairs absent after treatment compared with the number before treatment. For each site, at each follow-up visit, hair loss was calculated. Results for each experimental condition were pooled for all participants. The mean