Effectively Treating Ethnic Skin

But treating darker, ethnic skin types has always been particularly challenging because of the broad absorption spectrum of melanin. This has particular relevance as current projections show that the U.S. population will become more ethnically diverse, with greater than 35% of the population classified as non-white by 2010.1 In particular, the demand for laser hair removal has been in the forefront of research and development as more patients with varied skin types are seeking treatment. Initially, hair removal technology was limited to lighter skin types because of the risk of pigment alteration, pain, scarring and poor efficacy in darker skin types. With the advent of effective skin cooling methods (pre-, parallel and post-treatment), varied wavelength capabilities and the ability to adjust pulse duration parameters, a new era in hair laser for ethnic skin types has begun. Hair Removal Principles Current hair-removal laser technology targets the individual hair follicle using endogenous melanin as its primary chromophore. Melanin is found in the hair matrix, hair shaft, follicular epithelium and the epidermis. Effective hair removal requires selective absorption of light energy by the melanin in the hair shaft and adequate thermal conduction to two important target sites, which include the germinative cells of the hair matrix and papilla and follicular stem cells located near the insertion of the arrector pili muscle.2 The goal and the challenge with ethnic skin types is to deliver enough fluence to the target areas that affect re-growth and cause hair reduction without causing epidermal damage. The thermal relaxation time (TRT) is the time it takes for substantial cooling of a given site within the skin. The epidermis has a TRT estimated to be 3 msec to 10 msec, with the deeper target areas in the 40 msec to 100 msec range.3 Larger structures release heat more slowly than smaller structures, so the hair shaft and follicle can absorb and hold more heat longer than smaller epidermal structures.4 To achieve selectivity in the target areas (for example, the hair follicle), you must apply laser energy in a pulse duration that approximately equals the TRT of the hair follicle but exceeds the TRT of the epidermal melanin. Effective Treatment in Ethnic Skin Types Hair lasers that operate in the red or near infrared wavelengths, where selective melanin absorption occurs, include: • 694 nm ruby • 755 nm long pulsed alexandrite • 800/810/983 long pulsed diode • 1064 nm long pulsed Nd:YAG.5 It’s difficult to treat darker, ethnic skin types because the melanin in the epidermis acts as a competing chromophore. One of the first lasers on the market for hair removal was the ruby laser. The ruby laser (694 nm) is well absorbed by melanin — more than four times as well absorbed as the Nd:YAG laser (1064 nm). The long pulse ruby laser works well on lighter skin types with dark hair and has some effectiveness in ethnic skin types;7 however the higher concentration of melanin in ethnic skin types makes effective use of the ruby laser difficult. This was confirmed in a review article that demonstrated that 29% of patients with varied skin types experienced hypo- or hyper-pigmentation after treatment with the long pulsed ruby laser.8 The Data on Longer Wavelength Lasers We know that melanin absorbs energy less efficiently as the wavelength moves closer to the infrared spectrum, therefore the longer pulse wavelengths would have less affinity for epidermal melanin and more energy would reach the deeper follicular structures.8 The longer wavelength lasers can penetrate 5 mm to 10 mm into the dermis, twice that of the ruby laser.5 This has led to a variety of studies on longer wavelength lasers used to treat ethnic skin types, which have shown good results and reduced epidermal pigment alteration. Chan and colleagues compared the 1064 nm Nd:YAG with the 800 nm diode in treating 15 Chinese females with unwanted hair growth in the axilla and legs after one treatment session.9 There were few side effects on both treatment sites, and an impressively low regrowth rate at 6 weeks (23% and 19% respectively), which jumped to 91% re-growth at 36 weeks.9 Other authors showed that more effective epilation was possible with multiple, rather than single, treatments using either the 1064 nm Nd:YAG or the 800 nm diode laser.10 Alster11 showed that after three treatments with the 1064 nm Nd:YAG laser with cooling, 20 female patients with skin types IV – V experienced a 75% reduction in hair regrowth with long-term benefits witnessed.11 Long-term hair reduction results in skin types I – V were markedly improved (27% vs. 50%) after two, instead of just one, treatments with the Nd:YAG laser.12 Adrian and colleagues showed, via retrospective data analysis, effective and well-tolerated hair epilation in more than 200 treatment sites for skin types V – VI with the long pulse 1064 nm Nd: YAG lasers.13 The above studies demonstrate efficacy using longer wavelength lasers. Which is the Laser of Choice? The 1064 nm Nd:YAG laser is the laser of choice for very dark-skinned patients with coarse, dark hair; however, as the absorption of epidermal melanin decreases so does the absorption of follicular melanin.5 In theory, although safer for the darkest skin types and coarsest hair, the 1064 nm lasers may require more treatment sessions and may be less effective on less melanin-rich targets such as lighter or finer hairs than the 800 nm diode, 755 nm alexandrite and 694 nm ruby lasers.. Only long-term follow-up will settle this question. Practically speaking, the number of treatments is not only dictated by the laser wavelength used, but by the skin and hair type of the individual patient, fluence used, pain tolerance of the patient, treatment site and pulse duration. The ruby laser provides too much energy absorption; and although effective on dark coarse hair, the long pulsed Nd:YAG doesn’t provide enough absorption for treating moderately dark or finer hairs effectively and efficiently. So what about the 755 nm alexandrite and 800 nm diode lasers? Initially, side effects for treating varied skin types using the alexandrite and the ruby laser were shown to be similar despite the variation in wavelength.8 But this wasn’t the case when the pulse duration of the alexandrite was lengthened. Longer pulse durations allow enough time for heat to slowly build within the hair follicle and cause damage and enough time for heat to dissipate from the epidermal melanosomes without injury.8 This means that if the pulse duration is increased along with the fluence, the risk of epidermal damage is minimized while hair response is maximized. An ex vivo study compared varying pulse durations (30, 200 to 1,000 msec) using an 810 nm diode laser, which showed that thermal damage was similar with pulse durations between 30 msec to 400 msec with the same fluence. But beyond this, results were dependent on the fluence used and were without increased benefit.14 Garcia and colleagues showed minimal side effects (less than 2%) in 150 patients with skin type IV – VI when using a 40 msec pulse duration with a 755 nm alexandrite laser and fluences based on skin response. There was a 40% reduction in hair count after three treatments.4 Keeping It Cool Skin cooling is particularly important when treating darker, ethnic skin types as more epidermal absorption of energy can cause greater epidermal damage and pigment changes. Several methods of cooling can be used, including: • cryogen spray • glide contact • air-cooling • parallel contact cooling. Parallel contact cooling devices — firing the laser through a chilled sapphire plate in contact with the skin — cool the skin before, during and after each pulse of energy is delivered and appear to offer some advantages. Advantages include better epidermal protection because of the heat extracted during the pulse. Longer pulse durations (20 msec to 100msec) with the 800 nm diode laser and contact skin cooling not only allow substantially higher fluences to be used for all skin types (I – VI), but reduce the incidence of pigment and textural changes that can be seen at these higher settings.15 Reda and colleagues demonstrated that using the 755 nm long pulse alexandrite with dynamic cooling produced a 49% to 54% hair reduction with only 10% to 11% incidence of side effects in skin types IV and V.16 Garcia and colleagues showed that although the 755 nm long pulse alexandrite laser appeared to have a complication rate as low as 2.7% when treating skin types IV – V, treatment with this laser in skin type VI patients was contraindicated due to adverse effects.4 Despite longer pulse durations and cooling devices, which appear to help attain better results with the alexandrite laser system, the wavelength appears to result in a higher than acceptable incidence of side effects in darker skin types. Getting the Right Mix The proper combination of wavelength, pulse duration and effective skin cooling is paramount in treating ethnic skin types. The newer 800/810/983 nm long pulse diode lasers with adjustable pulse durations and aggressive skin cooling mechanisms may address the complexities of effective hair removal in darker ethnic skin types. Barolet and colleagues compared the 808 nm and 893 nm long pulse diode lasers in patients with skin type I – IV, and demonstrated that while both lasers affected the consistency and texture of the hair, the 808 nm patients maintained better long-term results (8 months).17 The 810 nm diode with a 50 msec pulse duration used to treat 24 female patients with skin type II - IV showed an impressive 74% hair removal at 3 months with minimal side effects noted.18 Similar hair reduction results (70%) were shown using an 800 nm diode laser on skin types I - V.19 A small study looking at only skin types V – VI being treated with an 810 nm diode laser had amazing results with 75% to 90% hair reduction after 7 to 10 treatments. There was minimal pigment change that resolved in less than 4 months.20 The 800 nm diode laser with a cool sapphire tip and pulse durations of 30 msec is quite effective in skin types II – VI. But it may still produce some degree of short-term side effects, such as erythema, perifollicular edema, blistering and/or crusting, which could possibly lead to transient hypopigmentation. Several of these side effects that are seen in darker, ethnic skin types can be minimized with several techniques: • application of a chilled clear water-based gel prior to treatment use • careful cleansing and shaving of the treatment area • prior exfoliation of the skin (with mild glycolic acids) if folliculitis is a problem • use of 4% hydroquinone as a skin bleaching agent before and after treatment (to prevent or treat pigment changes) • strict use of a sun block between treatments to minimize additional epidermal melanin stimulation • application of topical corticosteroids post treatment to reduce inflammation • adjustment of fluence for hair density and careful spacing of pulses. Growing Ethnic Populations Effective and efficient hair removal in ethnic skin types is particularly timely and important given the current demographic shifts and the excessive hair growth patterns sometimes evident in many ethnic populations. Although classified into the Fitzpatrick skin types for historical comparison, some ethnic skin types are more complex than the Fitzpatrick scale. Kono and colleagues studied the response in Japanese patients to an 800 nm long pulse diode laser with contact cooling.21 The patients were classified as Fitzpatrick skin types II – IV, although the authors mention that a specific “Japanese Skin Type” (JST) conversion was made, and they demonstrated greater than 60% hair reduction in 50% of the patients with minimal and transient side effects.21 This delineation of skin types to include ethnic influences was acknowledged when Battle and colleagues established a new classification scale based on skin color and ethnicity and labeled it the Ethnic Skin Type (EST).15 These researchers showed that the 800 nm long pulse diode laser with contact cooling and a longer pulse duration (100 msec) allowed higher fluences to be used for greater long-term hair loss in all ethnic skin types (I – VI).15 A particularly beneficial application of diode lasers in darker, ethnic skin types has been in the treatment of pseudofolliculitis barbae (PFB). PFB, an inflammatory condition that results from coarse hair turning back toward the skin or piercing through the hair shaft rather than follicular orifice, occurs primarily in African-American and Hispanic patients.2 This condition can be cosmetically bothersome and potentially disfiguring, but it had no effective treatment options until the advent of laser hair removal. Use of the long pulse 810 diode laser with a 30 msec pulse duration showed complete resolution in all patients with a history of PFB.20 The concerns for ethnic skin types also apply to the “tanned” Fitzpatrick skin types (I –IV) as we have seen in our beachside Florida practice. Our Laser Choice Although no current laser is perfect for treating ethnic skin, the best ones seem to be the long pulse 1064 nm Nd:YAG and the 800/810 nm long pulse diode lasers. These lasers have several advantages. First, their specific wavelengths deeply penetrate the hair follicle (but limit epidermal damage). Second, they adjust their pulse duration and their contact cooling mechanisms. The 800/810 nm long pulse diode appears to have a slight advantage with the depth of penetration/effective energy deliverance (efficacy) with minimal epidermal effects. We’ve shown the benefits and safety profile of the Apex 800 nm long pulse diode laser with aggressive subzero sapphire tip contact cooling (Iridex Corporation) in treating darker skin types (Poster Session, ASLMS 2002). We conclude that the 1064 nm Nd:YAG laser is best for skin type VI, but the 800 nm diode laser is more versatile and effective on a wider range of patients who have darker skin types.