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Removal of Bikini Hair Using a Rapid 810-nm Diode Laser Madeline C. Krauss, Md
The efficacy, safety, and treatment time of a new, high-speed, very long-pulsed (90–200 ms) 810-nm diode laser have been evaluated for the rapid removal of bikini hair. Study participants (n520) received 5 treatments at 6-week intervals. Hairs were counted from pretreatment and posttreatment photo-graphs. Among the 16 people who completed the study, the median hair count at 6 months after the fifth treatment was significantly lower than the median pretreatment hair count (P,.0001). The median hair count reduction fractions increased after the second treatment and continued to increase at 3- and at 6-month follow-up visits, indicating continual improvement. Hair count reduction fractions achieved a median of 87.6% (mean584.4%) at 6 months after the final treatment. Adverse effects were not observed, and treatment time was short. The 810-nm diode laser has been observed to safely and efficiently remove unwanted hair from the bikini area. Unwanted hair has traditionally been removed The application of SP for laser hair removal was first by wax, tweezers, shaving, chemical depil- described in 1996 by Grossman et al.6 Since then, use of atories, or electrolysis. These techniques the ruby, alexandrite, Nd:YAG, and diode laser devices are time consuming, monotonous, painful, for hair removal have been evaluated and reviewed and have limited efficacies.1 Electrolysis, in detail.7,8 once a popular procedure for permanent hair removal,1,2 is The purpose of the study described in this article was to invasive, tedious, and only partially effective and can result evaluate the efficacy and safety of a new, high-speed, very in scarring or postinflammatory hyperpigmentation.2 long-pulsed 810-nm diode laser for the rapid removal of Laser and light-based devices offer alternatives to tra- ditional physical methods and have gained considerable
popularity. In 2006, removal of hair by a laser device Materials and Methods
was the third most frequently performed nonsurgical In this prospective study, 20 women aged 19 to 59 years
cosmetic procedure in the United States.3 Laser and (median age 44.0 years) with Fitzpatrick skin types I to
light-based modalities destroy hair follicles by selective III were treated in the bikini area for 5 times at 6-week
photothermolysis (SP),4 in which melanin in the hair intervals with a continuous-wave 810-nm diode laser
shaft and surrounding follicular epithelium is the target device that protects the epidermis during treatment by
chromophore. When red and near-infrared wavelengths both contact (sapphire) and air (Zimmer) cooling. The
penetrate deeply into the dermis and are selectively Zimmer cooling device, set to level 4, was attached to
absorbed by melanin, thermal damage is restricted to the the head of the 810-nm diode laser and did not require
hair follicles as a result of SP.5
a second operator. To encourage study participants to return for their 6-month follow-up visit, an additional Dr. Krauss is in private practice, Wellesley, and Faculty Member, treatment was given at this final visit after photographs Newton Wellesley Hospital, Newton, Massachusetts. and hair count data were obtained. The 6-week interval Dr. Krauss is a speaker for and has received a stipend from between treatments was chosen to permit regrowth of hair in the treated areas.9,10 Participants had either black 392 Cosmetic Dermatology® • jULY 2008 • VoL. 21 No. 7
2008, Quadrant HealthCom Inc. All rights reserved maximum fluence for participants was 60 j/cm2. In all treatments, the spot (ie, beam) was rectangular and mea- Fluences and Pulse
sured 12310 mm. The treatment head was moved over Durations Available on
each area without overlapping, using a small amount the 810-nm Diode Laser
of aqueous ultrasound gel. Unlike circular beams, rect-angular beams do not require overlapping to cover the entire treatment area. The repetition rate with both pro- Pulse Duration, ms
grams was 3 Hz. Lidocaine 4% was applied to the treated Fluence, J/cm2
Program I Program II
areas 30 to 60 minutes before each treatment by the par-ticipant. Treatment time for each site ranged from 5 to 7 minutes. Posttreatment care was not necessary. Hairs were counted from the marked areas on the photographs just before the first and third treatments, 3 months after the final treatment, and 6 months after the final treatment. Six months was chosen for the final follow-up to approximate the length of the growth cycle of a single hair.11 In this way, we measured long-term hair reduction rather than short-term posttreatment hair loss due to temporary injury to the follicles.
Differences in 6-month hair counts from pretreatment or brown hair. They provided signed informed consent to values were evaluated with the Wilcoxon signed rank test, participate, and the study was conducted according to the a nonparametric alternative to the paired samples t test. principles outlined in the Declaration of Helsinki. Hair reduction fractions were calculated by subtracting The participants had received no laser or electrolysis the hair count at a given treatment from the pretreatment treatments prior to the study, did not tan or use self tanners hair count, and dividing that number by the pretreatment
during the study, did not shave for 3 weeks before the first hair count.
treatment and before 3-month and 6-month follow-up
visits, and did not wax in the treated areas. Shaving results
was permitted during the study but not electrolysis and of the 20 participants, 16 completed the study. Four
waxing. Anatomic reference points were marked on withdrew for personal reasons unrelated to efficacy or the
areas of skin measuring 9 cm2, which were then pho-
adverse effects of treatment. Because hair count values tographed and used for hair counts. The treated areas were not all normally distributed, data were analyzed and were immediately photographed with a 35-mm digital expressed nonparametrically as medians and interquartile camera, and the photographs were used to obtain a ranges (IQRs). The IQR is the difference between the 75th count of the hair strands immediately before the first and 25th percentiles and is a measure of dispersion. The and third treatments and 3 and 6 months after the final median and IQR hair count values were 70.5 and 46.8, (fifth) treatment. respectively, before the first treatment; 35.0 and 22.2, Combinations of fluence and pulse duration were respectively, just before the third treatment; 19.0 and 7.8, available in 2 programs (Table). Participants with respectively, at 3 months; and 11.0 and 8.2, respectively, Fitzpatrick skin types I and II were treated with program I, at 6 months. starting at a fluence of 40 j/cm2 and increasing by The median hair reduction fractions increased after the 4 j/cm2 at each subsequent visit unless adverse effects second treatment and continued to increase at 3- and at or excessive redness developed. Pulse duration was 6-month follow-up visits (Figure 1). The median hair varied automatically from 90 to 136 ms, with increas- count at 6 months was significantly lower than the median ing fluence. Participants with Fitzpatrick skin type III pretreatment hair count (P,.0001). Median hair count were treated with program II, starting at a fluence of reduction fractions increased to 87.6% (mean584.4%) at 36 j/cm2 and increasing by 4 j/cm2 with each subsequent 6 months after the final treatment. Clinical examples are treatment unless adverse effects or excessive redness shown in Figures 2 and 3. developed. The pulse duration was varied from 120 to Although pain during treatment was not specifically 200 ms. Some participants with Fitzpatrick skin assessed, no participant asked to stop the procedure or type III were changed from program II to program I withdraw from the study because of discomfort. Pigmen-for the duration of the study after the second or third tation changes, blistering, and paradoxical hair growth treatment, thereby shortening the pulse duration. The were not observed in any participant.
VoL. 21 No. 7 • jULY 2008 • Cosmetic Dermatology® 393
2008, Quadrant HealthCom Inc. All rights reserved Removal of Bikini HaiR
times. However, as shown in Figure 1, the pres- ent study found that 5 treatments with the new 810-nm diode laser removed approximately 87% of hair in the bikini area after 6 months. This clearance rate is higher than the 78% clearance rate achieved after 5 treatments with the alexan-drite laser after 1 year.10 The 810-nm diode laser is designed to opti- Hair Reduc
mize hair removal by careful configuration of wavelength, spot size, pulse duration, and flu-ence. The 810-nm wavelength and large spot size allowed for deep penetration, good melanin absorption, and avoidance of excessive competi- Treatment Visit
tion from other chromophores.17 In addition, the large spot size and high repetition rate led to very Figure 1. Median hair reduction percentages before treatment, after 2 treat-
short treatment times of 5 to 7 minutes per par- ments, 3 months after the final treatment, and 6 months after the final treatment. ticipant. The short treatment times allowed for PreTx indicates pretreatment; Tx2, 2 treatments; FU, follow-up. many participants to be treated in a single day, which added to participant satisfaction because the short duration of the procedure made it easier to The efficacy and safety of diode lasers for the long-term tolerate comfortably. removal of hair has been shown.12-18 Repetitive treatments For a laser or light-based device, treatment time is have been found to provide greater hair reduction than a determined by the coverage rate, which is the product single treatment13 at 20-month follow-up, and treatment of the area of the spot and the repetition rate.26,27 In outcomes are comparable with those obtained with the our study, the 810-nm diode laser spot was rectangu-alexandrite laser19 and Nd:YAG laser.20 lar, measuring 12310 mm, so the area of the spot was The bikini area has been treated with the alexandrite 120 mm2. Since the repetition rate was 3Hz, the cover- laser,10,21 normal-mode ruby laser,22 long-pulsed ruby age rate is 360 mm2/s. The coverage rate of a comparable laser,23 Nd:YAG laser,24,25 and diode laser.14,15 Clinical 800-nm diode laser device used for hair removal may be results were supported by histologic data in 2 studies.15,24 similarly calculated. In the study of Lou et al,13 the spot It is difficult to compare the results of the present of the 800-nm laser device was square shaped, measur- study with those of other studies because of the different ing 939 mm. Since the maximum repetition rate of this methods of assessing hair removal, the differences in the device is 2 Hz,5 the coverage rate is 162 mm2/s, less than number of treatments, the lack of specific data on hair half of the coverage rate of the 810-nm diode laser used in removal from the bikini area, and the different follow-up the present study. A square spot measuring 12312 mm, Figure 2. The bikini area of a 44-year-old female before treatment (A) and at 6-month follow-up (B) who achieved an 84.8% reduction in hair
counts after 5 treatments with the 810-nm diode laser.
394 Cosmetic Dermatology® • jULY 2008 • VoL. 21 No. 7
2008, Quadrant HealthCom Inc. All rights reserved Removal of Bikini HaiR
Figure 3. The bikini area of a 42-year-old female before treatment (A) and at 6-month follow-up (B) who achieved an 87.9% reduction in hair
counts after 5 treatments with the 810-nm diode laser.
or 144 mm2, has also been used in published studies of In our study, the epidermis was protected during treat-the 800-nm diode laser.5 With this larger spot, the cover- ment by both contact (sapphire) and air (Zimmer) cool- age rate increases to 288 mm2/s, which is still lower than ing. The sapphire device also compressed the dermis the 360 mm2/s of the 810-nm device. The shorter treat- and its blood vessels, which decreased the distance ment time is an even greater advantage when the 810-nm between the laser and the follicle11 and decreased inter-diode laser is used to treat body areas larger than the ference from hemoglobin.
bikini area, such as the back and legs. Long-pulse durations have been the topic of additional The rectangular shape of the spot of the 810-nm diode investigations. Eremia and Newman31 suggested that laser device permits a shorter treatment time than a tra- although pulse widths of 30 to 100 ms may exceed the ditional circular spot. With a circular beam, a minimum TRT of coarser hairs, longer 100- to 1000-ms pulses may of 17% beam overlap is required to cover the entire treat- actually increase efficiency by providing another pathway ment area.26 Therefore, the calculated coverage rate for a to injuring different areas of the follicles. In most treat-circular beam must be multiplied by 0.83 to correct for ments of the present study, pulse durations fell within the the overlap. Circular beams are used in the alexandrite suggested 100- to 1000-ms range. lasers,21,28,29 Q-switched Nd:YAG lasers,30 ruby lasers,12,29 Rogachefsky et al32 used a super long-pulsed 810-nm diode laser to remove hair from the legs and neck. These The pulse durations of previous studies with the diode investigators introduced the concept of thermal dam- laser are 5 to 20 ms,14 5 to 30 ms,13,18 and 80 to 100 ms.15 age time, which is the time needed for delivered laser Since the thermal relaxation time (TRT) of hair follicles energy to diffuse from the treated hair to the follicular- 200 to 300 µm in diameter is estimated at 40 to 100 ms associated hair stem cells. Thermal damage time ranged and the TRT for the epidermis is 3 to 10 ms,6 a pulse from 170 to 1000 ms, with fluences ranging from 23 to duration of 20 ms would appear to optimize the selective 115 j/cm2. optimal hair reduction 6 months after 1 or destruction of the hair follicle because 20 ms lies between 2 treatments was observed at 400 ms.
the TRTs of the epidermis and hair follicles.10,21 The limitations of our study are that the results were The pulse durations of our study (90–136 ms and not compared to results from other studies with untreated 133–200 ms) are longer than those used in previous controls, hair counts were not obtained by a blinded eval-
studies. However, pulse durations between 50 and uator, and treated areas were marked, but not tattooed, as
100 ms may result in heat diffusion during the laser suggested by Baugh et al.15
pulse and significant damage to the epidermis and
superficial dermis. To overcome this potential limitation ConClusion
and reduce pain during treatment, Ross et al11 suggested The 810-nm diode laser was observed to safely and effi-
the use of active conductive epidermal cooling, such as ciently remove unwanted hair from the bikini area. How-
cold water in a sapphire window. Cooling also permits ever, further studies with more participants are needed to
the use of higher fluences to damage the hair follicle.15 confirm these results.
VoL. 21 No. 7 • jULY 2008 • Cosmetic Dermatology® 395
2008, Quadrant HealthCom Inc. All rights reserved Removal of Bikini HaiR
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396 Cosmetic Dermatology® • jULY 2008 • VoL. 21 No. 7
2008, Quadrant HealthCom Inc. All rights reserved

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