Laser Hair Removal

Surgical Therapy

Laser-assisted hair removal is accomplished by destroying the follicular unit and thus inhibiting future hair growth by the follicle. The ability to accomplish this without damaging any surrounding tissue is based on the theory of selective photothermolysis. The theory states that at a particular wavelength (in nm), pulse duration, and fluence matrix, lasers or other light sources with wavelengths within the absorption spectrum of melanin are effective for hair removal. Typically the pulse duration, or length of time the pulse of light is emitted, should be shorter than or equal to the thermal relaxation time (TRT) of the target. The TRT of a hair follicle is from 10-100 milliseconds. However, pulses longer than the TRT of the hair shaft allows thermal damage to occur in the hair matrix stem cells and ensure follicular destruction. In order to minimize the risk of thermal damage to surrounding skin cells, cooling devices may be used to chill the skin before or during laser treatment.

Laser Systems

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), 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.⁵

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."

Long-pulsed ruby

The long-pulsed ruby laser was the first widely used laser for hair removal. Its 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.

Long-pulsed alexandrite

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.⁵ Studies have reported hair reduction from 4-56% after only a single treatment and from 33-95% hair reduction after multiple treatments, depending upon 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.

Long-pulsed diode

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.⁶

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.⁷ 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.

Preoperative Details

A large discrepancy can exist between patient expectations of treatment with laser-assisted hair removal systems and the actual effects of such a treatment. Open communication must exist between the care provider and the patient. A body surface area does not realistically remain completely hair-free after a single laser-assisted hair removal treatment.

Expectations

• Approximately 80% of all patients respond well to laser hair removal therapy.
• Patients should be counseled to expect a 30% decrease in hair at the treatment area with each laser treatment.
• Patients should understand that multiple treatments are often necessary to achieve the desired reduction in hair at a given body area. A minimum of 5 treatments is often necessary to achieve optimal patient satisfaction.
• Treatments are typically spaced 1-3 months apart.
• Individual response to laser-assisted hair removal is highly variable and depends upon numerous factors, including skin color, hair color and size, laser type, fluence, wavelength, and skin preparation.
• Laser hair removal is not without risk. Some discomfort may be associated with the procedure. Patients must also understand the potential for adverse effects, adverse reactions, and complications of laser treatment for unwanted hair.
• The best candidate for laser hair removal is a patient with light skin and dark hair.

Skin preparation and safety

• Patients should be instructed to avoid sunlight and active tanning prior to treatment. Bleaching of the skin with retinoic acid or hydroquinone can lighten the skin prior to laser treatment.
• Patients may shave or use depilatory creams up to the day prior to treatment, leaving hairs within the follicle and below the skin surface.
• Topical anesthetic creams or cryogenic sprays may be applied to the treatment area to reduce discomfort during the procedure. Cold compresses are also effective in reducing discomfort, erythema, and edema at the treatment area.
• The skin surface must be thoroughly cleansed of all makeup, anesthetic creams, and other applicants immediately prior to laser treatment. This may be done with water, followed by alcohol swabs, and should be allowed to dry completely.
• Laser systems are dangerous hazards to the eye. The highest concentration of melanin in the body is contained in the retina, which is highly susceptible to damage by laser light. Every person in the room during laser treatment should wear protective eyewear that is certified for the wavelength of the laser in use. Because the patient usually lies supine, he or she may require full occlusive eye protection to prevent laser light from entering underneath a sunglasses or goggle type of protective eyewear.

Intraoperative Details

Optimal outcomes of laser-assisted hair removal are obtained with the highest fluences, appropriate pulse duration, and the largest laser spot size. Test spots may be performed prior to treatment of larger areas to determine to highest fluence tolerated by the individual patient and the laser's effect on surrounding skin. The amount of fluence used should also depend upon the area of the body to be treated and the density of hairs at the site.

• In areas with thick, dense hairs, such as the beard area or upper back in men or the bikini area in women, a lower fluence should be used until the hair has sufficiently thinned. Epidermal damage could otherwise occur, due to the additive thermal energy absorbed by the higher density of hair follicles.
• When treating the brow area on men or women, the skin should be pulled up and away from the eyes and should overlay a flat portion of the forehead. This helps minimize the risk of laser light exposure to the eye and retina.
• A higher occurrence of adverse effects and adverse reactions has been noted at the neck region in women; higher fluences in this area should be used with caution.
• For treatment of the chin, perioral region, or upper lip, tooth enamel should be protected from excessive laser light exposure. Inappropriate exposure to certain laser light may induce hard tissue disintegration in the tooth and irreversible damage to dental pulp.

To minimize the possibility of thermal damage to skin and to improve patient comfort, the skin should be cooled during laser-assisted hair removal. As previously stated, all FDA-approved laser systems have an epidermal cooling device incorporated into the handpiece. Incorporated cooling mechanisms currently in use include cryogen sprays, sapphire-cooled hand pieces, and cold airflow.

• Cryogen sprays are used in short bursts prior to each pulse of laser light. Increasing the length of cryogen spurts can decrease the pain felt by the patient.
• A pre-cooled, heat-sinked sapphire window or water-cooled glass window can be incorporated into the laser handpiece. This comes into contact with the skin to be treated and cools the skin.
• Some laser handpieces contain a source of continuous cooled air. This cold air is blown over the area to be treated and cools the skin during laser treatment.
• Cold compresses or ice packs may be used prior to treatment, along with cooled laser handpieces. These may be applied prior to treatment or intermittently during a longer treatment time.
• Application of a cooled gel (eg, ultrasound, aloe vera) to the skin can aid in minimizing discomfort and epidermal damage. All gel must, however, be thoroughly removed from the skin prior to treatment.

A recent study has introduced a pneumatic skin flattening (PSF) device as an alternative to the dynamic cooling devices that are currently used.⁸ This device generates negative pressure on a small area of the patient’s skin, elevating and flattening the skin onto a sapphire window in preparation for laser therapy. This feeling of pressure against the skin may block the sensation of pain experienced by the patient. Study results thus far show that this method of treatment can be successful.

During laser treatment, each laser spot should overlap by no more than one third of the spot size. Further overlapping of continuous pulses causes accumulation of thermal injury and potentially causes epidermal damage. No overlapping of spots could result in missed areas in the treatment area. A treatment grid could be applied to the patient's skin and used as a guideline to outline the treatment area. With experience, the laser operator becomes proficient in visually tracking the treatment area.

Postoperative Details

• Immediately after a treatment session, patients should be given a cold compress or ice pack to decrease pain and reduce swelling. This effectively reduces discomfort, edema, and erythema, and keeps epidermal adverse effects to a minimum.
• Patients may also be given a topical corticosteroid cream to decrease local erythema.
• If minor skin damage has occurred, a topical antibiotic ointment may be applied until the skin has sufficiently healed.
• For more serious skin damage, an oral antibiotic may be prescribed for prophylaxis if deemed necessary by the health care provider.
• Makeup may be applied to treated areas the day following the procedure, as long as no epidermal damage has occurred.
• Patients should be told that hair casts will shed from treated areas over the following week and that this should not be confused with new hair growth.

Follow-up

Future treatments should be planned when they are likely to be most effective. Timing depends upon the body surface area to be treated. Hair on the trunk and extremities grows more slowly than on the face and head, and future treatments to the trunk and extremity should be planned after 2-4 months. In women, facial hair is lighter in color and finer in texture than on other parts of the body. These hair properties make the face a resistant area to treatment. Therefore, greater numbers of treatments are often required, and at shorter intervals. Treatments of the face should be timed at intervals of approximately 4-6 weeks.

Complications

Immediate effects after a single treatment of laser-assisted hair removal include perifollicular erythema and edema. These are expected after treatment and should not be considered adverse effects. They are minimized by cold application and resolve in a few hours.

The risk of developing adverse effects or complications after laser-assisted hair removal varies widely and depends upon many factors. The type of laser used may contribute to the incidence of adverse effects.

• The highest incidence of adverse effects has been reported to occur in patients with darker skin who were treated with the long-pulsed ruby laser.
• For individuals with darker skin, the long-pulsed diode laser and the long-pulsed Nd:YAG laser are recommended, and the Nd:YAG laser has been shown to have the least incidence of adverse effects.⁹

The incidence of adverse effects was reported after laser-assisted hair removal was performed on 480 patients. Reported adverse effects included (from highest to lowest incidence) blistering, hyperpigmentation, scabbing, hypopigmentation, scar formation, and thrombophlebitis.

• Blistering appears to be the most common adverse reaction and has been reported after treatment with all of the laser systems in use today over various skin tones. Blistering is a result of injury to the epidermis, possibly due to high fluences or increased overlapping of laser pulses.
• Scab formation is also a common adverse effect of laser treatment, due to epidermal damage. Blistering and minimal epidermal crusting have been reported in up to 15% of patients treated with both ruby and alexandrite lasers. These occurrences are more common in patients with tanned skin and darker skin types.
• Hyperpigmentation is a darkening of the skin and can occur after laser treatment. This phenomenon is usually reversible and is due to a stimulation of melanin production in skin melanocytes. This reaction is similar to a suntan.
• Hypopigmentation, or lightening of the skin, can occur after laser treatments. This is caused by damage to the epidermal melanocytes after their melanin absorbs laser light energy, causing destruction of these cells. This type of damage may be permanent and occurs more commonly in patients with darker skin.