Aside from noting that skin of color is especially susceptible to laser-induced side effects, it is difficult to make any additional general statements about lasers and darker skin; it is important to note that response to light and trauma varies based on skin color and patient ethnicity. Due to the variability of response to light energy, one of the first steps in considering the use of lasers on ethnic skin is to gather information regarding the patient’s ethnic heritage. The clinician can use this information to create a treatment database that begins to correlate the similarities and differences of patients based on their ethnicity and skin color. With time, this information will become almost intuitive to the experienced clinician, making it easier to outline a treatment approach for each individual patient.

Understanding the role of melanin is key to understanding both the desired and possible adverse effects of lasers. Melanin absorbs light over the majority of the photobiological wavelength spectrum; higher melanin levels lead to increased absorption of light energy. In patients with darker skin types, melanin in the skin can absorb significant amounts of light, which it then converts to heat. When the skin temperature surpasses 45^oC, laser induced thermal side effects occur (e.g. blistering, discoloration and scarring).  In addition to posing risks of adverse effects, higher melanin levels could interfere with the intended results of laser therapy. As melanin competes with the target chromophore, it reduces the amount of energy delivered to the target, thus reducing efficacy.

Laser Advancements
When they first widely emerged in dermatology during the 1990s, lasers were mainly used only on lighter skin types due to concerns of cutaneous side effects such as scarring, textural irregularities and dyspigmentation. However, research revealed that longer wavelengths and pulse durations coupled with efficient cooling devices drastically improved the ability of clinicians to safely and efficaciously treat darker skin types. Successful treatment of darker skin types relies on four key factors:

Longer wavelengths. The absorption spectrum for melanin ranges from 250-1200nm. Melanin absorption decreases as wavelengths get longer. Therefore, the longer the wavelength of the laser, the less melanin absorption.  Also, longer wavelengths penetrate more deeply into the skin, thus somewhat sparing the epidermis.

Longer pulse durations. Longer pulse durations deliver light more slowly, decreasing the speed of absorption by epidermal melanin. Subsequently, the epidermis heats up more slowly. Coupled with epidermal cooling, it is possible to keep the temperature of the epidermis under the 45^oC thermal injury threshold.

Epidermal cooling. Efficient cooling devices that aggressively remove heat from the epidermis are essential to minimize thermal damage, but success requires balance. Excessive use of cooling devices on pigmented skin can itself produce unwanted side effects, such as dyspigmentation. Cooling devices can be contact, which directly touch the skin, or non-contact, which emit a coolant-type spray, air or gas. 

Clinician knowledge. Any clinician who treats darker skin types must possess a firm understanding of laser physics as they apply to skin of color: the correlation between wavelengths, pulse durations, and skin cooling and their impact on epidermal temperature and subsequently epidermal damage. Finally, the clinicians must be prepared to effectively minimize post-treatment erythema, which can progress to post-inflammatory hyperpigmentation in darker skin types, and to immediately and effectively manage any adverse effects as they develop.

Laser-Assisted Hair Removal
With early lasers, the ideal hair removal candidate had fair skin and dark hair. This is no longer true. Patients of all skin types can now benefit from laser hair removal, which is fast, efficacious, and results in a permanent reduction of hair. The availability of laser-assisted hair removal is a welcome development for patients of color, who would otherwise have to rely on conventional hair removal methods—electrolysis, waxing, plucking, threading, depilatories. In addition to lack of convenience, all of these interventions  carry a very high incidence of side effects (dyspigmentation and scarring)  when used on darker skin tones and curly hair. As an added patient benefit, in addition to hair reduction, today’s so-called “color blind” hair removal lasers offer the benefit of providing dramatic improvements in the texture, tone, and evenness of color of treated skin.  Compared to fair skinned patients, darker skinned patients may require a few more treatment sessions to achieve permanent hair reductions—seven to up to 10 treatments.

The melanin deposits in the hair shaft and bulb represent the target chromophore in laser-assisted hair removal. Darker, coarser hair is an ideal primary target for laser energy. The more pigment the hair shaft has, the more light it absorbs, leading to greater heat induction and thermal damage.

Of course, epidermal melanin represents an unintended chromophore. When a longer-wavelength laser is used, the hair shaft and bulb preferentially absorb more laser energy, converting it to destructive heat, while epidermal melanin does not compete as strongly for absorption at these longer wavelengths. The diode lasers (810nm) and the Nd:YAG laser (1064nm) are both FDA cleared for laser-assisted hair removal in phototypes IV–VI. These longer wavelengths allow a greater depth of penetration to the intended follicular melanin chromophore with less absorption within the epidermis.

With the appropriate parameters (fluence, spot size), longer-wavelength laser-assisted hair removal devices are safe and effective to treat hair in darker skin types. Side effects such as blistering, crusting, and dyspigmentation usually result only when inappropriate parameters are set, i.e. fluences are to high, pulse durations are to short, and/or there is inefficient epidermal cooling.

In addition to contact- and non-contact cooling devices, adjunctive strategies can enhance epidermal cooling. Application of ice packs, cooled gel, air blowers, etc., all aid epidermal cooling.  Note that when using contact cooling lasers, the more slowly you administer treatment, the longer these devices are in contact with the skin, thus making cooling more effective.

Specific Patient Concerns
The two most common presentations for laser-assisted hair removal are hirsuitism and hypertrichosis. Patients require multiple laser treatments, performed at one to two month intervals. Each treatment produces about a 20 percent reduction in the amount of hair with resulting hair appearing finer and lighter-colored. Patients often experience a welcome and dramatic improvement in both skin texture and color (reduction in dark spots) following laser treatments.

Laser-assisted hair removal can also prove helpful in the management of hair-related skin conditions, such as pseudofolliculitis barbae (PFB). Because laser hair removal could produce a permanent “bald” look, patient counseling is important prior to treating the beard area of men. Patients who find this cosmetically unacceptable should not undergo laser-assisted hair removal.  A high incidence of PFB occurs on the neck and upper cheeks, so permanent removal of hair in these areas is often welcome without interfering with the natural beard or stubble look. Again, patients may experience welcome improvements in texture, tone, and color.  

Several general tips will guide treatment to enhance patient safety and improve outcomes:

Table 1. Estimated Treatment Times and Follow-up
By Body Site
Entire face:   15-20 minutes   1-2 months
Underarms:  10-15 minutes    1-2 months
Bikini area:   15-20 minutes    1-2 months
Legs:            45-90 minutes    1.5-2 months
Arms:            45-60 minutes    1.5-2 months
Back & shoulders:  60-120 minutes 1.5-2 months

Sidebar: Why You Should Consider Expanding Your Cosmetics Practice
Dermatologists increasingly recognize a need to meet the unique skincare needs of people of color. From developing and prescribing appropriate medical interventions for all manner of dermatoses to outlining safe and effective cosmetic services and procedures, the specialty is responding to a fast-growing demand. Estimates suggest that within five years, 40 percent of the population in the US will be comprised of people of color.

Like the population in general, patients of color are growing older. Younger professionals to retirees are interested in a wide array of services to help them maintain a youthful, rejuvenated appearance. From topical cosmeceutical products to laser interventions, patients of color represent a significant potential revenue opportunity for the cosmetic dermatologist. Furthermore, the knowledge and skill that practitioners acquire as they treat a wider range of patient skin types will only enhance the quality of service they provide all patients.

Eliot F. Battle, Jr., MD is co-founder and director of laser surgery for Washington DC’s Cultura Cosmetic Medical Spa (culturamed.com)—a medical practice merging dermatology, laser surgery, plastic surgery, and spa therapy. His laser research at Harvard helped to pioneer the new generation of non-invasive “color blind” cosmetic lasers, and he specializes in laser treatments on darker skin types. He is also Assistant Clinical Professor, Department of Dermatology, Howard University Hospital, Washington, DC.