A brief history of hair removal

Though hair has long served its purpose in ultraviolet protection and thermal regulation, humans have a long history of desiring to remove excess hair. Hair removal techniques, including razors and depilatories, date back to ancient times. Ancient Egyptian men were known to shave both their heads and beards; not for vanity but for survival, given that a smooth head and beard reduced the enemy’s ability to use the hair as a handhold grip for decapitation in combat. In the Roman world, a clean-shaven man became the symbol of civilization and progress. The current trend in hair removal in the United States was sparked nearly a century ago with a 1914 Harper’s Bazaar advertisement campaign depicting underarm hair as unhygienic and unfeminine with the emerging trend of more revealing female fashion. Following the lead of the fashion world and cultural trends, those involved in hair loss noted several additions to the field of hair removal that had otherwise remained stagnant, depending solely on razors and depilatories that had been unchanged for several centuries. In 1916 came the invention of electrolysis, and in the 1940s came the invention of Nair, the most effective depilatory cream to date.

Laser hair removal devices were first developed in the 1970s; however, techniques were ineffective and painful, limiting use. In 1995, the US Food and Drug Administration approved the neodymium yttrium aluminum garnet (Nd:YAG) as the first laser for hair removal and, soon after, the first article on laser hair removal was published in the New England Journal of Medicine. Subsequently, dozens of different brands of hair removal lasers/lights have become available using several different wavelengths to induce reduction.

Techniques for hair removal/reduction

Physical methods to temporarily reduce unwanted hair include plucking, shaving, waxing, and electrolysis. These techniques are best used on limited body surfaces, because the side effects of irritation and pain are common. Hair loss is not permanent and frequent treatments are required to produce desired results.

Topically applied eflornithine 13.9% (Vaniqa) cream inhibits ornithine decarboxylase. It is approved for reduction of unwanted facial hair in women when applied twice daily. Hair growth is slowed but not eliminated. Patients must be appropriately counseled on medication compliance and slow onset of results.

Electrolysis uses electricity for the removal of unwanted hair. This removal is performed by passing low-flow direct current (DC) through tissue between 2 electrodes, resulting in tissue damage and destruction of hair follicles by the creation of a chemical reaction at the tip of the electrode. Electrons are released at the negatively charged electrode, producing hydrogen gas and hydroxide ions from water; the resultant hydroxides then chemically destroy the adjacent hair follicle. Nonphysician personnel performing electrolysis use pure galvanic or blended galvanic and high-frequency electrolysis, whereas medical professionals tend to prefer high-frequency electroepilation, which achieves faster results. Galvanic electrolysis is safer, less likely to scar, and less painful than high-frequency electrolysis but works slower. In order for hair removal to be permanent, the hair follicle root must be destroyed. To minimize risk of scarring, the superficial portion of the hair follicle is not treated. Good lighting and clean skin are required for best results, as is correct placement of the electrolysis needle. Use of an insulated needle limits heat generation to the base of the follicle only, minimizing damage to the upper perifollicular dermis and, therefore, decreasing risk of scarring. Use of timers allows for safe use of both insulating and noninsulating needles. Home-use, hand-held electrolysis devices are available and may be used for minimal areas of hypertrichosis and hirsutism.

Techniques for hair removal/reduction

Physical methods to temporarily reduce unwanted hair include plucking, shaving, waxing, and electrolysis. These techniques are best used on limited body surfaces, because the side effects of irritation and pain are common. Hair loss is not permanent and frequent treatments are required to produce desired results.

Topically applied eflornithine 13.9% (Vaniqa) cream inhibits ornithine decarboxylase. It is approved for reduction of unwanted facial hair in women when applied twice daily. Hair growth is slowed but not eliminated. Patients must be appropriately counseled on medication compliance and slow onset of results.

Electrolysis uses electricity for the removal of unwanted hair. This removal is performed by passing low-flow direct current (DC) through tissue between 2 electrodes, resulting in tissue damage and destruction of hair follicles by the creation of a chemical reaction at the tip of the electrode. Electrons are released at the negatively charged electrode, producing hydrogen gas and hydroxide ions from water; the resultant hydroxides then chemically destroy the adjacent hair follicle. Nonphysician personnel performing electrolysis use pure galvanic or blended galvanic and high-frequency electrolysis, whereas medical professionals tend to prefer high-frequency electroepilation, which achieves faster results. Galvanic electrolysis is safer, less likely to scar, and less painful than high-frequency electrolysis but works slower. In order for hair removal to be permanent, the hair follicle root must be destroyed. To minimize risk of scarring, the superficial portion of the hair follicle is not treated. Good lighting and clean skin are required for best results, as is correct placement of the electrolysis needle. Use of an insulated needle limits heat generation to the base of the follicle only, minimizing damage to the upper perifollicular dermis and, therefore, decreasing risk of scarring. Use of timers allows for safe use of both insulating and noninsulating needles. Home-use, hand-held electrolysis devices are available and may be used for minimal areas of hypertrichosis and hirsutism.

Laser/lights: overview

Laser epilation of unwanted hair is currently the most popular and effective way to achieve permanent to semipermanent reduction of hair. Laser hair removal is 60 times more effective, less painful, and requires fewer sessions than electrolysis.

The mechanism of action of laser epilation is dependent on selective photothermolysis of melanized hair through the absorption of light energy. The principal of selective photothermolysis was conceived by Anderson and Parrish in 1983. Selection of preferentially absorbed wavelength and delivery at appropriate fluence and pulse duration allows for destruction of target tissue with limited damage to surrounding tissues. Fig. 1 shows the absorption spectrum of hemoglobin and melanin and the corresponding wavelengths of commonly used lasers.

Absorption spectrum and laser wavelengths.

To maximize damage to the desired chromophore (melanin), light sources are chosen based on the wavelength(s) best penetrating into the dermis to the hair follicle where melanin is present, and using pulse duration shorter than or equal to the thermal relaxation time (the time required for heated tissue to lose 50% of its heat). Clean ablation of tissue is defined as the ability to ablate faster than the heat is conducted to surrounding tissue. Terminal hair follicles with a diameter of 300 μm have a thermal relaxation time of 100 milliseconds. Permanent hair removal requires damage to follicular stem cells in the bulge region of the hair follicle, whereas temporary hair loss is achieved through damage causing induction of catagen. Follicular stem cells are nonpigmented targets located at a distance from melanin chromophores in a pigmented hair shaft. To damage nonpigmented targets, heat must diffuse from the target chromophore to the nonpigmented desired portion. Miniaturization of terminal hairs results in vellus hair formation but not complete removal. Typical laser pulse durations range from 3 to 100 milliseconds. Complete degeneration of the hair follicle with fibrosis occurs with pulses of high energy greater than 20 milliseconds in the red to near infrared spectrum. Super-long pulse heating (>100 milliseconds) seems to allow for long-term hair removal. If the pulse width is too long, there is insufficient time for heat to dissipate, and an undesirable temperature increase occurs with resulting thermal injury to nonfollicular structures that may lead to scarring or pigment irregularities. The ideal pulse duration in laser hair removal is approximately 10 to 50 milliseconds, which is between the thermal relaxation time for the epidermis (3–10 milliseconds) and that for the hair follicle (40–100 milliseconds); this varies based on terminal follicle diameter.

Another variable that can be adjusted in laser technique is spot size. Spot size, the width of the laser beam, is approximately 4 times the width of the target depth, because larger spot sizes allow for less effect of scatter as the laser interacts with the tissue. Hair removal lasers/lights have spot sizes of 8 mm up to several centimeters. Assuming other factors are stable, a larger spot size penetrates more deeply and may improve efficacy by targeting terminal hair follicles located deep in the dermis and subcutis.

Given that melanin is the chromophore, or target, for selective photothermolysis, hair shafts lacking melanin (blond or white hair) respond poorly to laser hair removal and this technique is therefore inappropriate. The best candidates for laser hair removal are dark-haired, fair-skinned patients. Laser hair removal can be performed on tan or darkly pigmented skin but with an increased risk of postinflammatory hyperpigmentation or hypopigmentation. Certain wavelengths or devices, such as Nd:YAG devices, are safer in dark skin types (see later discussion). Because only anagen follicles are susceptible to thermal injury, all protocols for laser/light hair reduction call for multiple sessions in a period of months to attain successful outcomes. Properly timed and dosed treatments to a given area generally result in incremental reduction in hair density after each treatment, but, even after many treatments, an area will continue to grow at least some hair.

The best results with long-term laser hair removal have been shown to correlate with the amount of eumelanin pigment in the hair follicle. To improve results in fair-haired individuals, additional exogenous chromophores including dyes, photosensitizers, and carbon particles have been used. Most recently, studies have been with the use of liposome technology to deliver melanin to the hair follicle. Liposomes are phospholipids (the biologic lipids of cell membranes) that spontaneously adopt bilayers in water. Melanin-encapsulated liposomes have been shown to selectively deliver melanin to the hair follicle and shaft. The studies published to date of liposomal melanin spray have been mixed.