Since the first lasers were approved for the use of hair removal in 1996, dramatic advances have occurred in laser technology. This has led to the development of several laser types for the treatment of unwanted hair. Before the widespread use of longer wavelengths and pulse durations and more effective cooling devices, laser-assisted hair removal was best used to treat individuals with light skin and dark hair. More recently, however, long-pulsed lasers have been used to safely and effectively treat patients with darker skin types. Laser light sources currently used to destroy hair photothermally include the long-pulsed ruby (694 nm), long-pulsed alexandrite (755 nm), a long-pulsed diode (810 nm), and long-pulsed neodymium:yttrium-aluminum-garnet (Nd: YAG, 1064 nm). The efficacy of these different lasers for treatment of unwanted hair and the frequency of adverse effects encountered after treatment have been compared in various skin types.
The efficacy of each of the following laser systems is compared in terms of permanent hair reduction. Hair reduction, as defined by the FDA, “refers to a significant reduction in the number of terminal hairs after a given treatment, which is stable for a period of time longer than the complete growth cycle of hair follicles at the given body site.”
The long-pulsed ruby laser was the first widely used laser for hair removal. It’s light energy has the most selective absorption by melanin and the shortest depth of penetration (wavelength of 694 nm). Use of this laser for hair removal is indicated in individuals with light skin and dark hair. Its efficacy in individuals with light skin has been demonstrated in numerous studies, ranging from 20-60% hair reduction after one treatment and up to 50-78% reduction after multiple treatments. The ruby laser penetrates the skin by only 1-2 millimeters and can cause significant absorption by epidermal melanin of thermal energy. In studies treating a wide range of skin types with the ruby laser, more adverse reactions have occurred in patients with darker skin. The use of this laser on patients with darker skin types is not recommended.
The 755-nm alexandrite laser has now been widely used for laser hair removal and is recognized as being efficacious and generally safe. This laser is still typically used for patients with lighter skin types, but its longer wavelength allows for deeper penetration into the skin, and it can be used for patients with darker skin.Studies have reported hair reduction from 4-56% after only a single treatment and from 33-95% hair reduction after multiple treatments, depending upon a number of treatments and body location. The adverse effects of this laser, when used on patients with darker skin types, can include blistering, crusting, and alterations of pigment, even when skin cooling devices are used. In patients classified as having the darkest skin, residual hypo- or hyperpigmentation is the rule with the alexandrite laser.
Treatment of unwanted hair with the 810-nm long-pulsed diode laser has been demonstrated as comparable to those of the ruby or alexandrite lasers. After a single treatment, hair reductions of 32-34% have been reported, and up to 84% hair reduction has been reported after multiple treatments. The diode laser has a longer wavelength and adjustable pulse duration, and, when used with an efficient skin-cooling device, allows for the treatment of patients with darker skin types. The diode laser is more effective for laser-assisted hair removal in patients with dark skin because of the higher absorption by melanin than is seen with the Nd: YAG laser. Still, temporary adverse effects have been reported with the use of the diode laser in the form of postinflammatory hyperpigmentation when used on individuals with dark skin.
Long-pulsed Nd: YAG
The Nd: YAG laser is the safest type used to treat unwanted hair on patients with dark skin and is most suitable for patients in this group. At 1064 nm, this laser penetrates the skin deeper than other lasers (to a level of 4-6 mm) with less absorption at the skin, but it is also less effectively absorbed by melanin. This leads to lower instances of adverse effects and better tolerance in patients with dark skin, but also lower efficacy for hair removal. Permanent hair loss has been reported, however, with reported hair reductions of 27-53%, depending on the number of treatments administered and the body location.
The FDA has approved the long-pulsed diode and the long-pulsed Nd: YAG lasers for use in hair removal in patients with darker skin classifications. All FDA-approved laser systems used for hair removal must have efficient and effective epidermal cooling devices incorporated as part of the system.
Intense pulsed light systems
Pulsed, noncoherent broadband light sources are now accepted and widely used in the medical industry for hair removal and other applications. Intense pulsed light (IPL) systems utilize a xenon bulb as a light source, which produces polychromatic light with wavelengths from 550-1200 nm. This is in contrast to laser light sources, which produce monochromatic light of a specific wavelength. Light emitted by the bulb passes through a filter that excludes shorter wavelengths that may severely damage skin. The ability to “tune” the wavelength of light emitted by these systems gives IPL systems the advantage of versatility. Using different filters, a pulsed light system could mimic any number of laser systems, allowing the operator to treat many different conditions amenable to light therapy, including, of course, the removal of unwanted hair.
Studies have shown intense pulsed light to be an effective method of hair removal. In a study of 210 patients who underwent hair removal by IPL, a mean hair reduction of 80% was reported after 3-5 treatments. Minimal adverse effects, including transient erythema and localized edema, were reported.
The variability of light output can also be a disadvantage of IPL systems. The light spectrum may vary slightly with each pulse, and reproducibility of treatments varies between operators. The handpieces of IPL systems are typically larger than laser-based systems, which makes treatment of fine areas of the skin difficult.
Author: Christian N Kirman, MD, Staff Physician, Department of Plastic and Reconstructive Surgery, Wake Forest University Baptist Medical Center Coauthor(s): Joseph A Molnar, MD, PhD, FACS, Associate Professor of Plastic and Reconstructive Surgery, Associate Director, Burn Unit, Wake Forest University School of Medicine; Samer Alaiti, MD, FACP, Clinical Assistant Professor, Departments of Dermatology and Internal Medicine, University of California at Los Angeles School of Medicine; Medical Director, Miracle Mile Medical Center for Dermatology and Cosmetic Surgery, Inc Contributor Information and Disclosures
Updated: Nov 6, 2008