• Diode Hair Removal - White Papers

    • Study

      Removal of Bikini Hair by 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 by wax, tweezers, shaving, chemical depil- atories, or electrolysis. These techniques are time consuming, monotonous, painful,

      and have limited efficacies. Electrolysis,

      once a popular procedure for permanent hair removal,1,2 is invasive, tedious, and only partially effective and can result in scarring or postinflammatory hyperpigmentation.2

      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 was the third most frequently performed nonsurgical cosmetic procedure in the United States.3 Laser and light-based modalities destroy hair follicles by selective photothermolysis (SP),4 in which melanin in the hair shaft and surrounding follicular epithelium is the target chromophore. When red and near-infrared wavelengths penetrate deeply into the dermis and are selectively absorbed by melanin, thermal damage is restricted to the hair follicles as a result of SP.5

      The application of SP for laser hair removal was first

      described in 1996 by Grossman et al.6 Since then, use of

      the ruby, alexandrite, Nd:YAG, and diode laser devices

      for hair removal have been evaluated and reviewed

      7,8 in detail.

      The purpose of the study described in this article was to evaluate the efficacy and safety of a new, high-speed, very long-pulsed 810-nm diode laser for the rapid removal of hair from the bikini area.

      Materials and Methods

      In this prospective study, 20 women aged 19 to 59 years (median age 44.0 years) with Fitzpatrick skin types I to III were treated in the bikini area for 5 times at 6-week intervals with a continuous-wave 810-nm diode laser device that protects the epidermis during treatment by both contact (sapphire) and air (Zimmer) cooling. The Zimmer cooling device, set to level 4, was attached to the head of the 810-nm diode laser and did not require a second operator. To encourage study participants to return for their 6-month follow-up visit, an additional treatment was given at this final visit after photographs and hair count data were obtained. The 6-week interval between treatments was chosen to permit regrowth of hair in the treated areas.9,10 Participants had either black

      page1image30176 page1image30336

      Dr. Krauss is in private practice, Wellesley, and Faculty Member, Newton Wellesley Hospital, Newton, Massachusetts.

      Dr. Krauss is a speaker for and has received a stipend from Alma Lasers, Ltd.

      392 Cosmetic Dermatology® • jULY 2008 • VoL. 21 No. 7

      Fluences and Pulse Durations Available on the 810-nm Diode Laser

      Pulse Duration, ms


      Fluence, J/cm2


      Program I


      Program II



      or brown hair. They provided signed informed consent to participate, and the study was conducted according to the principles outlined in the Declaration of Helsinki.

      The participants had received no laser or electrolysis treatments prior to the study, did not tan or use self tanners during the study, did not shave for 3 weeks before the first treatment and before 3-month and 6-month follow-up visits, and did not wax in the treated areas. Shaving was permitted during the study but not electrolysis and waxing. Anatomic reference points were marked on areas of skin measuring 9 cm2, which were then pho- tographed and used for hair counts. The treated areas were immediately photographed with a 35-mm digital camera, and the photographs were used to obtain a count of the hair strands immediately before the first and third treatments and 3 and 6 months after the final (fifth) treatment.

      Combinations of fluence and pulse duration were available in 2 programs (Table). Participants with Fitzpatrick skin types I and II were treated with program I, starting at a fluence of 40 j/cm2 and increasing by 4 j/cm2 at each subsequent visit unless adverse effects or excessive redness developed. Pulse duration was varied automatically from 90 to 136 ms, with increas- ing fluence. Participants with Fitzpatrick skin type III were treated with program II, starting at a fluence of 36 j/cm2 and increasing by 4 j/cm2 with each subsequent treatment unless adverse effects or excessive redness developed. The pulse duration was varied from 120 to 200 ms. Some participants with Fitzpatrick skin type III were changed from program II to program I for the duration of the study after the second or third treatment, thereby shortening the pulse duration. The

      maximum fluence for participants was 60 j/cm2. In all treatments, the spot (ie, beam) was rectangular and mea- sured 12310 mm. The treatment head was moved over each area without overlapping, using a small amount 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- grams was 3 Hz. Lidocaine 4% was applied to the treated 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 values were evaluated with the Wilcoxon signed rank test, a nonparametric alternative to the paired samples t test. Hair reduction fractions were calculated by subtracting the hair count at a given treatment from the pretreatment hair count, and dividing that number by the pretreatment hair count.


      of the 20 participants, 16 completed the study. Four withdrew for personal reasons unrelated to efficacy or the adverse effects of treatment. Because hair count values were not all normally distributed, data were analyzed and expressed nonparametrically as medians and interquartile ranges (IQRs). The IQR is the difference between the 75th and 25th percentiles and is a measure of dispersion. The median and IQR hair count values were 70.5 and 46.8, respectively, before the first treatment; 35.0 and 22.2, respectively, just before the third treatment; 19.0 and 7.8, respectively, at 3 months; and 11.0 and 8.2, respectively, at 6 months.

      The median hair reduction fractions increased after the second treatment and continued to increase at 3- and at 6-month follow-up visits (Figure 1). The median hair count at 6 months was significantly lower than the median pretreatment hair count (P,.0001). Median hair count reduction fractions increased to 87.6% (mean584.4%) at 6 months after the final treatment. Clinical examples are shown in Figures 2 and 3.

      Although pain during treatment was not specifically assessed, no participant asked to stop the procedure or withdraw from the study because of discomfort. Pigmen- tation changes, blistering, and paradoxical hair growth were not observed in any participant.

      VoL. 21 No. 7 • jULY 2008 • Cosmetic Dermatology® 393

      Removal of Bikini HaiR




      Tx2 3 mo FU

      Treatment Visit

      6 mo FU

      Figure 1. Median hair reduction percentages before treatment, after 2 treat- ments, 3 months after the final treatment, and 6 months after the final treatment. PreTx indicates pretreatment; Tx2, 2 treatments; FU, follow-up.

      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- 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- tion from other chromophores.17 In addition, the large spot size and high repetition rate led to very short treatment times of 5 to 7 minutes per par- ticipant. The short treatment times allowed for many participants to be treated in a single day, which added to participant satisfaction because



      The efficacy and safety of diode lasers for the long-term removal of hair has been shown.12-18 Repetitive treatments have been found to provide greater hair reduction than a single treatment13 at 20-month follow-up, and treatment outcomes are comparable with those obtained with the alexandrite laser19 and Nd:YAG laser.20

      The bikini area has been treated with the alexandrite laser,10,21 normal-mode ruby laser,22 long-pulsed ruby laser,23 Nd:YAG laser,24,25 and diode laser.14,15 Clinical results were supported by histologic data in 2 studies.15,24

      It is difficult to compare the results of the present study with those of other studies because of the different methods of assessing hair removal, the differences in the number of treatments, the lack of specific data on hair removal from the bikini area, and the different follow-up

      the short duration of the procedure made it easier to tolerate comfortably.

      For a laser or light-based device, treatment time is determined by the coverage rate, which is the product of the area of the spot and the repetition rate.26,27 In our study, the 810-nm diode laser spot was rectangu- lar, measuring 12310 mm, so the area of the spot was 120 mm2. Since the repetition rate was 3Hz, the cover- age rate is 360 mm2/s. The coverage rate of a comparable 800-nm diode laser device used for hair removal may be similarly calculated. In the study of Lou et al,13 the spot of the 800-nm laser device was square shaped, measur- ing 939 mm. Since the maximum repetition rate of this device is 2 Hz,5 the coverage rate is 162 mm2/s, less than half of the coverage rate of the 810-nm diode laser used in 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

      Hair Reduction, %


      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.

      Removal of Bikini HaiR


      or 144 mm2, has also been used in published studies of the 800-nm diode laser.5 With this larger spot, the cover- age rate increases to 288 mm2/s, which is still lower than the 360 mm2/s of the 810-nm device. The shorter treat- ment time is an even greater advantage when the 810-nm diode laser is used to treat body areas larger than the bikini area, such as the back and legs.

      The rectangular shape of the spot of the 810-nm diode laser device permits a shorter treatment time than a tra- ditional circular spot. With a circular beam, a minimum of 17% beam overlap is required to cover the entire treat- ment area.26 Therefore, the calculated coverage rate for a circular beam must be multiplied by 0.83 to correct for the overlap. Circular beams are used in the alexandrite lasers,21,28,29 Q-switched Nd:YAG lasers,30 ruby lasers,12,29and Nd:YAG lasers.16,29

      The pulse durations of previous studies with the diode laser are 5 to 20 ms,14 5 to 30 ms,13,18 and 80 to 100 ms.15Since the thermal relaxation time (TRT) of hair follicles 200 to 300 μm in diameter is estimated at 40 to 100 ms and the TRT for the epidermis is 3 to 10 ms,6 a pulse duration of 20 ms would appear to optimize the selective destruction of the hair follicle because 20 ms lies between the TRTs of the epidermis and hair follicles.10,21

      The pulse durations of our study (90–136 ms and 133–200 ms) are longer than those used in previous studies. However, pulse durations between 50 and 100 ms may result in heat diffusion during the laser pulse and significant damage to the epidermis and superficial dermis. To overcome this potential limitation and reduce pain during treatment, Ross et al11 suggested the use of active conductive epidermal cooling, such as cold water in a sapphire window. Cooling also permits the use of higher fluences to damage the hair follicle.15

      In our study, the epidermis was protected during treat- ment by both contact (sapphire) and air (Zimmer) cool- ing. The sapphire device also compressed the dermis and its blood vessels, which decreased the distance between the laser and the follicle11 and decreased inter- ference from hemoglobin.

      Long-pulse durations have been the topic of additional investigations. Eremia and Newman31 suggested that although pulse widths of 30 to 100 ms may exceed the TRT of coarser hairs, longer 100- to 1000-ms pulses may actually increase efficiency by providing another pathway to injuring different areas of the follicles. In most treat- ments of the present study, pulse durations fell within the suggested 100- to 1000-ms range.

      Rogachefsky et al32 used a super long-pulsed 810-nm diode laser to remove hair from the legs and neck. These investigators introduced the concept of thermal dam- age time, which is the time needed for delivered laser energy to diffuse from the treated hair to the follicular- associated hair stem cells. Thermal damage time ranged from 170 to 1000 ms, with fluences ranging from 23 to 115 j/cm2. optimal hair reduction 6 months after 1 or 2 treatments was observed at 400 ms.

      The limitations of our study are that the results were not compared to results from other studies with untreated controls, hair counts were not obtained by a blinded eval- uator, and treated areas were marked, but not tattooed, as suggested by Baugh et al.15


      The 810-nm diode laser was observed to safely and effi- ciently remove unwanted hair from the bikini area. How- ever, further studies with more participants are needed to confirm these results.

      VoL. 21 No. 7 • jULY 2008 • Cosmetic Dermatology® 395

      Removal of Bikini HaiR


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      20. Eremia S, Li C, Newman N. Laser hair removal with alexandrite versus diode laser using four treatment sessions: 1-year results.Dermatol Surg. 2001;27:925-929.

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      23. Polderman MC, Pavel S, le Cessie S, et al. Efficacy, tolerability, and safety of a long-pulsed ruby laser system in the removal of unwanted hair. Dermatol Surg. 2000;26:240-243.

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      32. Rogachefsky AS, Silapunt S, Goldberg Dj. Evaluation of a new super-long-pulsed 810 nm diode laser for the removal of unwanted hair: the concept of thermal damage time. Dermatol Surg. 2002;28:410-414. n

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