Synopsis of Laser Assisted Hair Removal Systems

Hypertrichosis and Hirsutism

Hypertrichosis is defined as increased hair at any body site regardless of gender. Hirsutism is the presence of excessive hair at androgen dependent sites. Waxing, shaving, tweezing, chemical depilatories and electrolysis are traditional methods to eliminate unwanted hair. However, with the exception of electrolysis, these treatments are temporary. Laser hair removal offers an alternative method to permanently reduce excessive hair growth.

Methodology of Laser Hair Removal

Most laser treatment for hair removal is based on the principle of selective photothermolysis¹, which states that by choosing the appropriate wavelength, pulse duration, and fluence, thermal injury can be confined to the target chromophore. The chromophore of pigmented hair follicles is melanin, which is located primarily in the hair shaft and in the bulge². Whether damage to either one or both of these two sites is sufficient to produce permanent hair removal remains unknown. While early studies suggest that anagen hair is the most susceptible to damage by laser pulses, recent data confirms that hairs in all portions of the cycle may be targeted³. During the early anagen phase, the bulb and the bulge are in close proximity to each other and are located high within the dermis. Red and infrared laser light can easily penetrate and damage these structures altering hair growth. Each treatment reduces hairs by approximately 20%. As well, hairs become less dark and coarse⁴. The result of successive treatments is the miniaturization of terminal hairs into vellus hairs.

Treatment Guidelines

To obtain optimal results, the fluence must be tailored to the patient’s skin type. Scarring and pigmentary alteration may be seen with inappropriately high fluences and poor patient selection, and whitening, epidermal disruption and blistering are tissue responses that indicate inappropriately high fluences. Because these findings can be immediate or delayed, it is important to carefully observe the treated areas for at least five minutes before proceeding with a full treatment.

The ideal patient for laser hair removal is light skinned with black coarse hair. Blonde, gray and white hairs do not respond to treatment. Dark skinned individuals, and especially tanned patients are at high risk for pigmentary alterations. Cooling devices, either spray or contact, are helpful for protecting the epidermis, but may not be sufficient to protect tanned or darker skinned patients. Patients with a tan should delay treatment until the tan fades. Darker skinned patients are best treated with long pulsed wavelength lasers such as the diode (800 nm) or the new long pulsed Nd:YAG lasers (1064 nm).

A history should be obtained to search for any underlying medical or preventable cause for excessive hair growth, e.g., tumor or drug. Individuals with a history of hypertrophic scarring or keloids should be treated with caution. Those who have been treated with isotretinoin should wait at least one year before undergoing laser treatment. Patients should not pluck or wax 2-4 weeks prior to treatment. Bleaching hair does not interfere with treatment because the intracutaneous portion of the darkly pigmented hair is not affected. A bleaching cream can be applied to the area six weeks before treatment for patients with skin types III and higher to prevent pigmentary alteration.

Topical anesthesia may be used to prevent discomfort, but local infiltration is rarely necessary.

After the procedure, ice packs may be needed to reduce edema and pain. A mild potency topical corticosteroid is usually applied for two to three days posttreatment to reduce perifollicular edema and erythema. Sun avoidance is a must. Patients should be told that they might experience some shedding of the treated hair within the first few weeks of treatment and this should not be confused with regrowth. Loss of freckles in the treated area is possible.

Infection is rarely seen except when there is epidermal damage. Although herpetic outbreaks are uncommon, patients at the highest risk can be protected with antivirals.

Table 1. Laser Hair Removal Systems

Specific Laser Systems

The low energy Q-switched Nd:YAG laser (SoftLight by ThermoLase) used in conjunction with a carbon-containing topical solution produces only temporary hair loss. High energy, short pulsed Q switched Nd:YAG lasers produce some permanent hair growth reduction, but are not as effective as the long pulsed laser systems. However, they can be used safely on darker skinned individuals.

The EpiLaser and EpiPulse by Palomar Medical Technologies and ESC Sharplan, respectively, are long-pulsed ruby lasers (694 nm) with pulse durations in the millisecond domain. The long pulsed ruby lasers produce permanent hair loss after 1-2 years of treatment, which histologically correlates with miniaturization of the hair bulb and papillae5. Pigmentary side-effects are most common at this wavelength because it is so well absorbed by melanin.

Long pulsed alexandrite lasers (755 nm) produce less pigmentary side-effects, and while long-term studies have yet to be completed, results suggest that hair removal is as effective as the ruby lasers.

Diode lasers (800 nm) produce long-term hair reduction similar to the ruby lasers with less pigmentary side-effects. Because of the longer pulse duration, it is more effective for coarse hair, but slightly less effective for fine hair. The intense pulsed light source (EpiLight by ESC Sharplan) delivers an incoherent broad spectrum of light that can be used with filters to narrow the range wavelengths emitted at pulse durations of 2.5-7 ms. The broad wavelengths of this device are theoretically more effective for a variety of hair colors in both light and dark skin types⁴.

Conclusion

Laser hair removal is a safe and relatively effective therapeutic option for patients who desire permanent reduction of hair growth. Early studies suggest permanence, but only time will tell how truly effective these devices are. The aim of technical advances in the future include permanent loss of hairs of all color, and safety of use on all skin types after just one treatment.