Optimizing Treatment Parameters for Hair Removal

Reprinted
from the Archives
of Dermatology
December,
1997 lib/ume 133
Copyright
1997, American Medical Association
--------------------------------------~IIIIIIaIIII~--------------------------------------
Optimizing Treatment Parameters for Hair Removal
Using a Topical Carbon-Based Solution and
l064-nm Q-Switched Neodymium:YAG_Laser Energy
Christopher A. Nanni, MD; Tina S. Alster, MD
Obiective: To determine the most effective treatment
parameters for laser-assisted hair removal using a Qswitched neodymium:yttrium-aluminum-garnet
(Nd:
YAG) laser.
Design: Prospective study to determine the effectiveness of Q-switched Nd:YAG laser-assisted hair removal
under varying pretreatment protocols. Hair growth was
assessed after laser treatment, and the results were compared with those of wax epilation at 4, 12, and 24
weeks.
Selling:'A private ambulatory
demic referral center.
laser facility and aca-
Intervention: Laser-assisted hair removal was performed under 4 different pretreatment conditions. Eighteen areas of unwanted body and facial hair from 12 study
subjects were divided into 4 quadrants. Wax epilation
followed by application of a carbon-based solution and
exposure to Q-switched Nd:YAG laser radiation was performed on 1 quadrant. A second quadrant was wax epilated and exposed to Q-switched Nd:YAG laser radiation without prior carbon solution application. A third
quadrant was exposed to laser radiation alone, and a final quadrant was wax epilated to serve as the control.
Follow-up evaluations at 1,3, and 6 months consisted
of photographic documentation,
patient hair-density estimates.
Main Outcome Measure: Percentage of hair regrowth as assessed by objective hair counts and patient
subjective evaluations.
Results: Mean percentage of hair regrowth at 1 month was
39.9% for the wax-carbon-laser quadrant, 46.7% for the waxlaser quadrant, 66.1% for the laser-alone quadrant, and 77.9%
for the wax control quadrant. The percentage ofhairregrowth
approximately doubled by 3 months but was significantly
delayed in all laser-treated quadrants regardless of pretreatment protocol. Full hair regrowth in all anatomic locations
was observed by month 6. Patient subjective evaluations of
hair density closely approximated hair count data. No adverse effects or long-term complications were observed.
Conclusions: A single hair-removal treatment with the
Q-switched Nd:YAG laser is safe and effective in delaying hair growth for up to 3 months. Although the combination of pretreatment wax epilation and topical carbon solution application was effective, laser irradiation
alone, with or without wax epilation, also provided a significant delay in hair growth.
Arch Dermato!' 1997;133:1546-1549
L
From the Washington Institute
of Dennatologie Laser SurgelY,
Washington, DC.
ASER TECHNOLOGY has been
used within the field of
medicine for close to 40
years. Modern-day lasers can
effectively and safely treat a
variety of cutaneous conditions, including vascular and pigmented lesions, scars,
wrinkles, and tattoos. The frontier of cutaneous laser medicine has expanded with
the recent introduction of laser-assisted
hair-removal techniques. Laser-assisted
hair removal is appealing because it offers a rapid, relatively painless method for
hair removal with minimal risk of scarring or other adverse effects. 1-5 Several lasers are currently under investigation for
hair removal including the Q-switched
ARCH DERMATOUVOL
1546
manual hair counts, and
133, DEC 1997
neodymium:yttrium-aluminum-garnet
CNd:YAG), long-pulsed ruby, and longpulsed alexandrite lasers.
In 1996, the Food and-Drug Administration approved a patented laser process (Softl.ight, Thermolase Corp, Lajolla,
Calif) for hair removal that irlcludes the
use of a Q-switched Nd:YAG laser after
pretreatment wax epilation and application of a carbon-based solution. The present study examines Q-switched Nd:YAG
laser-assisted hair removal and attempts
to determine
whether
the abovedescribed patented procedure is necessary for optimal laser hair removal. The
medical literature lacks any evidence that
the combination of wax epilation and car-
11IIWax + Carbon + Laser
11IIWax + Laser
SUBJECTS AND METHODS
100
Twelve subjects (3 men and 9 women; mean age, 32
years) were enrolled in the study. A total of 18 anatomic locations were evaluated, including 6 backs,
3 upper lips, 1 chin, and 8 legs. Potential subjects with
evidence of endocrine dysfunction, immune suppression, recent oral retinoid use, drug-induced
hypertrichosis, sensitivity to infrared light, photosensitivity, collagen vascular disease, or androgenproducing tumor were excluded. Skin type, sex, hairremoval history, and patient age were recorded. All
skin types were considered for inclusion, although
only skin types I through IV were represented. Only
subjects with black or brown terminal hair were
included.
A Q-switched Nd:YAG laser (Thermolase Corp)
was used at a fluence of 2.6 j/crrr', a wavelength of
1064 nm, a pulse duration of 50 nanoseconds, a 7-mm
spot size, and a pulse repetition rate of 10 Hz. Study
areas on the back and legs were divided into 3-cm2
quadrants using a standard template. Facial areas were
divided into I-crrr' quadrants using a smaller template. Treatment sites were placed in a linear fashion, with orientation and location randomized for each
anatomic area. Pretreatment protocol in 1 quadrant
consisted of wax epilation and carbon-based solution application (Thermolase Corp) with subsequent "laser irradiation using the above set parameters. A second quadrant was wax epilated (without
carbon solution) and exposed to laser radiation. A
third area was exposed to laser radiation without any
pretreatment waxing or carbon solution application. The last quadrant was simply wax epilated and
served as a control. Those sites pretreated with carbon solution retained a thin film of surface carbon
after gentle wiping of excess solution with dry gauze.
The pretreated skin was subsequently irradiated
within 15 minutes after the application of carbon
solution.
Evaluations at 1, 3, and 6 months after treatment consisted of consecutive photographic documentation using identical lighting, camera, and patient positioning (Mirror Image System, Virtual
Eyes Inc, Kirkland, Wash); manual hair counts; and
subjective patient hair-density estimates. Hair-density estimates were based on each patient's subjective evaluation using a scale of no hair growth,
minimal or moderate growth, and thick hair growth
as options.
The number of terminal hairs present after treatment were compared with baseline hair counts. The
percentage of hair regrowth was defined as the percentage of hairs that were present after treatment compared with baseline hair counts. Anatomic locations
were grouped and analyzed separately. The percentage of hair regrowth was calculated for each study
quadrant. Paired-difference t tests were used to compare treatments. Wilcoxon signed-rank tests of the
paired differences were also performed for confirmation. Hochberg improved Bonferroni procedure
was used to maintain a joint significance level of .05
for the 4 tests within a single time point.
ARCH DERMATOUVOL
1547
80
.x:
! 60
~
a:
~
40
20
Figure 1. Mean percentage of patient hair regrowth.
Waxing
+
Solution
+
Laser
Waxing
Alone
Waxing
+
Laser
Laser
Alone
Figure 2. A 45-year-old man with pigmented terminal hairs on the back
before treatment.
bon solution application followed by Q-switched Nd:
YAG laser irradiation is more effective than wax epilation alone. It is also unclear whether the timeconsuming and messy procedure of waxing and carbon
solution application is more efficacious than laser irradiation alone when used on hair-bearing skin. Therefore, the present study served to evaluate hair growth
within 3 laser-treated sites with differing pretreatment
protocols using a fourth wax-epilated site as a control.
RESULTS
Hair regrowth was evaluated by hair counts and subjective patient evaluations of hair density at each of the 3
follow-up visits (at 1, 3, and 6 months). The mean percentage of regrowth (Figure 1) at 1 month was 39.9%
(P<.OOl) for the wax-carbon-laser quadrants, 46.7%
(P<.OOl) forthe wax-laser quadrants, 66.1 % (P=.10) for
the laser-alone quadrants, and 77.9% for the wax control quadrants (Figure 2 and Figure 3). At the 3month follow-up, all laser-treated quadrants had significantly less hair regrowth than the control quadrant, with
a mean of79.1 % (P=.006) for the.wax-carbon-laser quadrants, 85.2% (P=.Ol) for the wax-laser quadrants, 86.3%
(P=.02) for the laser-alone quadrants, and 102.2% for the
wax control quadrants (Figure 4 and Figure 5). Each
percentage of regrowth was well approximated by a nor-
133, DEC 1997
o Laser Alone
11II Wax + Carbon + Laser
iim Wax + Laser
11IIControl
1
--
Thick
Growth
-
Moderate
Growth
Waxing
+
Solution
+
Laser
Waxing
+
Laser
Waxing
Alone
Laser
Only
Minimal
Growth
Gro~
Figure 3. Same area as in Figure 2 one month after Q-switched
neodymium:yytrium-aluminum-garnet
(Nd:YAG) laser treatment with various
pretreatment preparations using a wax-epilated region as a control.
Treatment areas demonstrate 20% regrowth in Waxing + Solution + Laser
site, 24% regrowth in Waxing + Laser site, 85% regrowth in Waxing Alone
(control) site, and 61% regrowth in Laser Only site.
No
~~
_
o
__
~
1
~~
_
3
__
6
Month
Figure 6. Patient hair-density estimates.
month follow-up evaluation. Several patients, however,
reported that their hair quality had changed after laser
treatment, the regrown hairs exhibiting finer texture and
lighter color. This change in hair quality could not be
easily judged by photographic analysis and therefore could
not be supported by objective data. Other than a transient folliculitis that developed in 3 wax-epilated test quadrants, no cutaneous pigmentary or textural complications developed after laser treatment.
COMMENT
Waxing
+
Solution
+
Laser
Waxing
+
Laser
Waxing
Alone
Laser
Only
Figure 4. Region seen in Figures 2 and 3 three months after 1 treatment.
Treatment areas demonstrate 35% regrowth in Waxing + Solution +
Lasersite, 40% regrowth in Waxing + Laser site, 94% regrowth in Waxing
Alone (control) site, and 77% regrowth in Laser Only site.
Waxing
+
Solution
+
Laser
Waxing
+
Laser
Waxing
Alone
Laser
Alone
Figure 5. Six-month follow-up photograph shows full hair regrowth in all
treatment areas.
mal distribution. All hypothesis tests and associated P values are 2 sided.
Patient subjective hair-density estimates reflected the
objective hair count data (Figure 6). Full hair regrowth occurred in all study quadrants based on hair
counts and patient hair-density
estimates by the 6-
ARCH DERMATOUVOL
1548
Hair removal has become a major research interest and
economic force within the field of cutaneous laser medicine. Laser systems with differing wavelengths, pulse durations, and energy densities are currently under development for hair removal, based largely on unproven
theories and vague mechanisms of action. While the
theory of selective photo thermolysis could be used to optimize wavelengths and pulse durations for laser epilation, the exact target within the hair follicle has yet to
be clearly established." The hair matrix, papilla, and bulge
are all potential areas of hair follicle vulnerability. However, without knowledge of a specific follicular target, it
becomes difficult to predict which laser wavelengths and
pulse durations will be most successful.
At the time of study initiation, only 1 laser-assisted
hair-removal device had been approved for use by the
Food and Drug Administration (the SoftLight system by
Thermolase Corp). This system uses energy from a Qswitched Nd:YAG laser following pretreatment wax epilation and application of a patented carbon-based topical solution. It provides an exogenous target chromophore
(eg, carbon) to which l064-nm-wavelength
laser light
has an affinity. The carbon is theoretically placed within
wax-epilated follicles, and laser-induced thermal and photoacoustic damage is subsequently produced within the
follicular structure. Selective damage, then, remains independent of the presence of endogenous melanin.
The results of this study suggest that after a single
Q-switched Nd:YAG laser treatment, a change within the
hair follicle is produced that results in a delay of hair regrowth. However, permanent hair removal (cessation of
hair growth in treatment areas for the lifetime of the pa-
l33, DEC 1997
- ~I
tient) was not achieved. All treatment sites exhibited full
hair regrowth by 6 months, with some patients demonstrating regrowth as early as 1 and 3 months. While the
ideal goal of laser-assisted epilation is permanence, the
results of this study are consistent with those of previous studies involving single-session laser hair removal.
Goldberg' reported that Q-switched Nd:YAG laser treatment and application of carbon solution provided a reduction in hair growth for up to 6 months. Grossman et
aP reported a delay in hair growth for a 6-month period
after long-pulsed normal-mode ruby laser irradiation. This
apparent lack of permanence after laser hair removal has
been disappointing, but not entirely unexpected, considering the vulnerability of hair to treatment at different phases in its growth cycle. Electrolysis, for example,
requires numerous treatment sessions to effect a permanent reduction in hair growth. 7In a similar manner, it is
quite possible that permanent epilation will emerge a reality only after multiple laser treatments.P Repeated laser injury to the hair follicle, which was not examined
in the current study, should be investigated. Future studies should also address the question of whether laser light
simply induces a prolonged telogen hair cycle or whether
irreversible follicular damage is possible. Ultimately, histologic examination of treated hirsute sites will be necessary to fully understand the mechanisms of laserassisted hair re~oval.
Although pretreatment with wax epilation and a topical carbon solution resulted in significant hair removal,
this protocol was not essential. All laser-treated sites
showed less hair regrowth at 3 months than the waxepilated control quadrants, suggesting that the laser energy can target the follicle without an exogenous carbon chromophore. However, because of the limited
number of anatomic regions treated in this study, we
lacked the statistical power to determine if a particular
pretreatment protocol was superior to another.
It is interesting to note that the quadrants that were
simply exposed to laser radiation without waxing or carbon solution did not show a significant reduction in hair
growth until the third month. This finding may be attributed to the fact that, in areas that were not wax epilated, laser irradiation caused the terminal hairs to whiten
but to remain in the follicles. Although the hair shafts
were injured, hair counts at 1 month included these depigmented hair shafts. By the third month, however, the
injured hairs had fallen out of the follicles and a significant reduction in hair counts was recorded.
While the results of this study suggest that wax epilation and/or carbon-based solution application is not essential to the laser-assisted hair-removal process, it is important to note that all study subjects had brown or black
hair. When blonde or white hair-bearing areas are being
treated, exogenous carbon pigment application may play
ARCH DERMATOUVOL
1549
Printed
and Published
a more important role in selectively targeting and concentrating laser energy into the follicle. Presumably,
melanocytes and melanin within the hair follicle and shaft
are the primary targets of Q-switched Nd:YAG laser energy when the laser treatment is used without a carbon
solution. These melanin-producing cells are located within
the hair matrix at the base of the follicle, the infundibulum, and sparsely within the outer root sheath.P" As there
are greater numbers of melanocytes within the hair follicle than there are within the epidermis, laser energy can
pass through the skin surface and be absorbed selectively
by follicular melanin." This selective process obviously becomes more problematic when lighter hair colors are being treated. Gray hair, for instance, has fewer melanocytes at the hair bulb, and blonde hair has a decreased
number of partially pigmented melanosomes as compared with black hair." Therefore, exogenous pigment in
the form of a carbon-based solution may be helpful in the
treatment of individuals with lighter hair colors.
In conclusion,
a single treatment with a Qswitched Nd:YAG laser results in a greater delay of hair
growth (up to 6 months) when compared with wax epilation alone. Regardless of the use of pretreatment wax
epilation or carbon topical solution, hair growth was decreased when compared with control (waxed) areas. Complete hair regrowth occurred by 6 months after a single
treatment, suggesting that further research is needed to
determine the optimal treatment intervals, energy settings, wavelengths, and pulse durations needed to achieve
longer-lasting or permanent laser-assisted hair removal.
Accepted for publication August 18, 1997.
Reprints: Tina S. Alster, MD, Washington Institute of
Dermatologic Laser Surgery, 2311 M St NW, Suite 200,
Washington, DC 20037.
REFERENCES
1. Goldberg OJ.Topical solution-assisted laser hair removal Lasers Surg Med. 1995;
suppl 7:47. Abstract.
2. Goldberg OJ. Topical suspension assisted laser hair removal: treatment of axillary and inguinal regions. Lasers Surg Med. 1996;suppI8:195. Abstract.
3. Grossman MG, Dierickx G, Farinelli W, et al. Damage to hair follicles by normalmode ruby pulses. JAm Acad Dermatol. 1996;35:889-894.
4. Grossman MG, Wimberly J, Dwyer P, et at. PDT for hirsutism. Lasers Surg Med.
1995;suppl 7:47. Abstract.
5. Alster TS. Manual of Cutaneous Laser Techniques. Philadelphia, Pa: LippincottRaven Publishers; 1996:128-134.
6. Anderson RR, Parrish JA. Selective photothermolysis: precise microsurgery by
selective absorption of pulsed radiation. Science. 1983;220:524-527.
7. Richards RN, Meharg GE. Electrolysis: observations from 13 years and 140,000
hours of experience. JAm Acad Dermatol. 1995;33:662-668.
8. McKee PH. Pathology of the Skin. London, England: Mosby-Wolfe; 1996:1.201.21.
9. Olsen EA. Disorders of Hair Growth. New York, NY: McGraw-Hili Book Go; 1994:
52-55.
133, DEC 1997
in the United
States of America
/