Lasers for hair removal are a fast-growing area in cosmetic dermatology.
Selective photothermolysis allows for targeting of specific chromophores while minimizing cutaneous damage.
Treatment of individuals should be individualized based on anatomical area, skin and hair color, by varying the wavelength, fluence, pulse duration, spot size, and cooling technique of the laser.
Adverse events to laser hair removal include post-treatment erythema, edema, blistering, hypo/hyperpigmentation, scarring, and skin infections.
Further standardized, well-controlled, and long-term studies are needed to establish the optimal treatment parameters for each laser for each patient demographic.
Introduction
Laser hair removal is the second most common nonsurgical procedure performed in the U.S. Patients and physicians need to have realistic expectations of results for laser hair removal. The level of hair reduction may vary widely amongst individuals. Lasers are advantageous because they are fast, safe, and effective when used appropriately. Complete hair loss is defined as a lack of regrowing hairs but can be temporary or permanent. The mechanism of selective photothermolysis allows lasers to target specific cutaneous chromophores while protecting the outer tissue. Active cooling devices, such as cryogen sprays and contact cooling devices help to minimize injury to the epidermis. |
The use of lasers for hair removal, or photoepilation, is becoming an increasingly popular trend in the arena of cosmetic dermatology. According to the American Society for Aesthetic Plastic Surgery (ASAPS), 1,566,909 laser hair removal procedures were performed in 2005, increased from 1,411,899 procedures just a year earlier.1,2 Only Botox injections are pe rformed more frequently for both women and men, according to the ASAPS’s list of the top five most popular nonsurgical procedures among Americans. Although there has been a decrease in total nonsurgical procedures among women and men from 2004 to 2005, laser hair removal was an exception with a 1.1% increase in women and about a 1.2% increase in men. Men accounted for about 15% of the total laser hair removal procedures that were performed. Furthermore, laser hair removal was listed by the ASAPS as the top nonsurgical procedure for people 18 and under and for people between 19 and 34 years old. Hair removal has historically been of great interest because excess hair, especially in patients with hypertrichosis or hirsutism, can be troubling both socially and psychologically.3 Past and present options for hair removal have included shaving, epilation, depilatories, electrolysis and now most currently, lasers.4 All methods for hair removal have side effects, but lasers are advantageous because they are fast, safe, and effective when used appropriately. With the increased desire for and availability of laser hair reduction around the world, it is necessary to evaluate the current indications and potential side effects of each laser.
The concept of hair removal was defined in 1998 by the US Food and Drug Administration (FDA), which allowed some manufacturers of hair removal lasers and flash lamps used for hair removal to use the term “permanent hair reduction.” The agency defined permanent hair reduction as, “The long-term, stable reduction in the number of hairs regrowing after a treatment regime. The number of hairs regrowing must be stable over a time greater than the duration of the complete growth cycle of hair follicles, which varies from 4 to 12 months according to body location. Permanent hair reduction does not necessarily imply the elimination of all hairs in the treatment area.”5 In addition, there needs to be a distinction made between permanent and complete hair loss. Complete hair loss is defined as a lack of regrowing hairs, but may be either temporary or permanent. Permanent hair loss is defined as a lack of regrowing hairs indefinitely. Hair removal with lasers usually produces complete but temporary hair loss for 1–3 months. After this time period, there is usually partial but permanent hair loss.6
The theory of selective photothermolysis dictates the process of laser hair removal. By varying specific parameters (wavelength, pulse duration, and fluence), specific cutaneous chromophores may be targeted while protecting the outer lying tissue.7,8 Applying this theory to laser hair removal, the wavelength should be the same as the target chromophore, the pulse duration should be less than the chromophore’s thermal relaxation time (TRT), and the fluence must be great enough to sufficiently destroy the chromophore.
In laser hair removal, the specific target is the endogenous chromophore melanin. Melanin is found in the bulb, bulge, and hair shaft of anagen hair. Lasers for hair removal must emit light within the absorption spectrum of melanin, 250–1,200 nm, to be effective.9 In addition, vascular reduction has also been proposed as a mechanism for long-term epilation.10 One obstacle to laser hair removal is that melanin resides in the epidermis as well. This is a twofold problem because epidermal melanin not only interferes with the laser’s treatment capabilities by detracting some of the laser’s energy, but can also cause damage to the epidermis. Because pigmentation of the hair and skin vary to such a great extent among patients, this is a difficult problem to resolve.
Active cooling is an excellent method to minimize injury to the epidermis. Many lasers today are equipped with cooling devices such as cryogen sprays or contact cooling devices. For example, the long-pulsed 694 nm ruby lasers have a cooling hand piece that is applied during treatment to lower the temperature of the skin and spare it from injury. This integrated cooling device pre-cools the skin prior to laser pulse delivery. The long-pulsed 755 nm alexandrite lasers utilize a variety of cooling mechanisms. These mechanisms include a cooling hand piece that allows a continuous flow of chilled air to the treatment area, and a dynamic cooling device that uses short (5–100 ms) cryogen spurts that is delivered to the skin surface through an electronically controlled valve. The 800 nm diode lasers use a sapphire-cooled handpiece that is placed in direct contact with the skin to cool the area. The 1,064 nm Nd:YAG lasers uses a variety of cooling mechanisms and is based on the laser used; currently available options include a chill tip cooling device, pulsed cryogen delivery to the skin, contact pre-cooling and air cooling. Finally, intense pulsed light uses a chilled handpiece that cools the skin and a transparent gel that provides optical coupling, as well as additional cooling.6 In addition to these methods, ice and refrigerated gels can also provide relief.11
Another way to limit thermal injury to the epidermis, in keeping with the theory of selective photothermolysis, is to use a pulse duration between the TRT of the epidermis (3–10 ms) and that of the hair follicle (10–100 ms).4,11 However, recent studies have sparked a reconsideration of the original theory suggesting a modification whereby the target isn’t destroyed by direct heating, but by diffusion from the pigmented area.11,12 This requires long pulses upwards of 100 ms known as superpulses. These superpulses would also damage other crucial targets, such as stem cells, which may be another factor for permanent hair reduction.9
The current market for laser hair reduction is growing so rapidly that the FDA has not maintained an up-to-date listing of all approved laser devices. Currently used lasers fall into one of four categories: the long-pulsed ruby laser (694 nm), the long-pulsed alexandrite laser (755 nm), the long-pulsed semiconductor diode laser (800–810 nm), and the long-pulsed Nd:YAG laser (1,064 nm). Additionally, the Intense Pulsed Light (IPL) system (515–1,200 nm) is approved as a safe and effective method for hair reduction (Table 1).
Table 1
Laser and intense pulsed light systems for hair removal
Laser | Method of hair removal | Example | Skin type | Hair color | Hair diameter | Type of hair removal | Hair reduction | Side effects |
|---|---|---|---|---|---|---|---|---|
Long-pulsed ruby lasers (694 nm) | Photothermal destruction | E2000 Epitouch Ruby Ruby Star Sinon | I–III | Dark to light brown | Fine and coarse | Long term hair removal | 38–49% hair reduction | Treatment pain, erythema, edema, hypopigmentation, hyperpigmentation, blistering, crusting, erosions, purpura, folliculitis |
Long-pulsed alexandrite lasers (755 nm) | Photothermal destruction | Apogee Gentelase Epitouch ALEX Ultrawave II/III Epicare Arion | I–IV | Dark to light brown | Fine and coarse | Long term hair removal | 74–78% hair reduction | Treatment pain, erythema, edema, hypopigmentation, hyperpigmentation, blistering, crusting, erosions, purpura, folliculitis |
Pulsed diode laser (800 nm) | Photothermal destruction | LightSheer Apex-800 SLP1000 MedioStar F1 Diode Laser | I–IV | Dark to light brown | Coarse | Long term hair removal | 70–84% hair reduction | Treatment pain, erythema, edema, hypopigmentation, hyperpigmentation, blistering, crusting, erosions, purpura, folliculitis |
Long pulsed Nd:YAG lasers (1,064 nm) | Photothermal destruction | CoolGlide Lyra Ultrawave I/II/III Athos Gentle Yag Varia Acclaim 7000 Smartepil II Dualis Vasculight Elite Profile Mydon | I–VI | Dark | Coarse | Long term hair removal | 29–53% hair reduction | Treatment pain, erythema, edema, hypopigmentation, hyperpigmentation, blistering, crusting, erosions, purpura, folliculitis |
Intense pulsed light source (515–1,200 nm) | Photothermal destruction | EpiLight Quantum HR Ellipse PhotoLight Estelux ProLite Spatouch Quadra Q4 SpectraPulse | I–VI | Dark to light brown | Coarse | Long term hair removal | 49–90% hair reduction | Treatment pain, erythema, edema, hypopigmentation, hyperpigmentation, blistering, crusting, erosions, purpura, folliculitis |
Q-switched Nd:YAG lasers | Photomechanical destruction | Softlight MedLite C6 | I–VI | Dark to light brown | Fine and coarse | Temporary hair removal | 50–66% hair reduction | Treatment pain, erythema, edema, hypopigmentation, hyperpigmentation, blistering, crusting, erosions, purpura, folliculitis |
Indications/Contraindications
Unwanted hair is a very common problem affecting individuals from all demographics. The ideal candidate for laser hair removal is a person with fair skin and dark terminal hair. Some contraindications include active cutaneous infections, history of keloid or hypertrophic scarring, history of recurrent infections, and active vitiligo and psoriasis in targeted areas. |
Indications
Excess hair is an extremely common problem affecting both men and women, of all ages, and can have deep social and psychological impact on the patient. Some scenarios associated with unwanted hair include patients with hirsutism or hypertrichosis, procedures that involve grafted donor sites, and transsexual transformations from male to female. The patient must have a realistic expectation of the results, as the level of reduction in hair varies from individual to individual. The ideal candidate for laser hair reduction is a person with fair skin and dark terminal hair.
Contraindications
Patients with active cutaneous inflammation, infection, or active sunburn should not be treated until the area has resolved. A history of keloids and hypertrophic scarring is not an absolute contraindication, but these patients should be treated less aggressively. Patients with a history of recurrent infections (e.g., herpes simplex and staphylococcal) should be started on prophylaxis to prevent outbreaks. Patients who are on hormonal therapy should be advised on the limitations of hair removal treatment. Also, people with certain skin conditions such as vitiligo and psoriasis should avoid laser hair removal in affected areas, as it may lead to koebnerization. Finally, patients taking minoxidil, or who have spouses taking this medication, should be warned that hair removal may be disrupted by the stimulating effects of this drug.6
Techniques
The lasers used in hair reduction include the 694 nm ruby laser, the 755 nm alexandrite laser, the 800 nm diode laser, and the 1,064 nm Nd:YAG laser. The intense pulsed light system is also used in hair removal. Some of the parameters that must be optimized for each patient include the wavelength, pulse duration, fluence, cooling technique, and spot size of the laser. Dark skinned individuals generally have more side effects from laser hair removal. Patients must be notified at least 6 weeks prior to treatment that they must not pluck, wax, or use electrolysis in the targeted areas. |
Pre-operative Management
Laser Treatment Approach
Obtaining an accurate patient history is very important when interviewing a patient who is considering laser hair removal. It is imperative to clarify the patient’s expectations, what medications they are currently taking, their history of scarring, whether or not there is a local infection in the targeted area, whether or not they have tried other hair removal strategies in the past, their endocrine status, and the amount of sun exposure they have had recently. Physical examination is also crucial and should involve evaluation of the patient’s skin color, skin condition, hair color, hair diameter, and hair density.
Once a patient is determined to be a good candidate for hair removal, certain pre-operative counseling must be done. The patient must be notified that at least 6 weeks prior to the laser treatment they must not pluck or use electrolysis in the areas that they would like to undergo treatment. They may, however, shave or use depilatory creams. It has been shown that greater hair loss occurs at shaven rather than epilated sites. In addition, the treatment area should not be exposed to the sun.6
A few days prior to the laser treatment, the patient should be instructed to shave or use a depilatory cream on the treatment site (Fig. 1). They should also be advised to start the use of prophylactic antiviral agents, if there is a history of recurrent HSV. On the day of treatment, the area must be cleaned and free of make-up. A topical anesthetic may be applied 1–2 h before the procedure.6
Fig. 1
Pretreatment of right axillary area 2 days after shaving, only anagen hairs present
Description of Techniques
Long-Pulsed 694 nm Ruby Laser
The ruby laser has the shortest wavelength of the lasers available for hair reduction. Emitting light at 694 nm, it has the best absorption by melanin but the shortest penetration depth. Theoretically, this would imply that the ruby laser should be the most effective at hair reduction under the right conditions, but it also means that there is a greater potential for epidermal injury.13 A cooling hand piece is concomitantly applied during treatment to lower the temperature of the skin and spare it from injury.
Campos et al. reported very favorable results for long-term hair reduction using higher fluences of this laser system, with an average follow-up time of about 8 months after the last treatment.14 Study patients who had received treatment with a higher mean fluence of around 46 J/cm2 displayed sparse regrowth, as compared with moderate regrowth in patients who had received a lower mean fluence of around 39 J/cm.2 While an increase in fluence may contribute to overall efficacy, it also increases the frequency of side effects, which may include post-treatment erythema, crusting, blistering, hypopigmentation, hyperpigmentation, and scarring.13 These side effects, especially pigmentary alteration and scarring, were much more commonly seen in darker skin, specifically skin types IV to VI.15 This is due to the fact that shorter wavelength leads to greater absorbance of the laser by skin melanin, which is more abundant in darker skin types. Consequently, studies with this laser primarily involve lighter skin patients.13 It should also be noted that using a ruby laser with a pulse duration of 1 ms (as compared to 20 ms) has proven to cause greater epidermal damage in patients with darker skin.16,17
Overall, most studies performed with the 694 nm ruby laser have shown it to be a safe and effective method for nonpermanent hair reduction.13 – 15,18,19 When comparing three treatments using the ruby laser with three treatments of waxing or electrolysis, it was found that the laser provided a 38–49% hair reduction while the alternatives provided no significant change.16,18 Increasing the number of treatments appeared to correlate with a decrease in overall hair count.16,18 – 21 Most of these studies have also noted better results in patients with light skin and dark hair.13,15,16 These patients respond well to the laser and experience fewer side effects because they have the ideal combination of profuse deposits of melanin in the hair with lesser amounts in the epidermis.14
Long-Pulsed 755 nm Alexandrite Laser
The long-pulsed alexandrite laser has a wavelength of 755 nm. This slightly longer wavelength allows a deeper penetration of the dermis with less absorption by epidermal melanin, theoretically making adverse side effects less of a concern for darker skin patients as compared to the ruby laser. However, studies indicate that blistering, hypopigmentation and hyperpigmentation were still reported occurred in some patients with darker skin types.13,15 Results have consistently shown good clearance rates for hair reduction.
Lloyd and Mirkov reported a 78% clearance of hair 1 year following five treatments (parameters were 10 mm spot size, 20 J, 20-ms pulse duration, and 3 week intervals) for their patients.22 Similarly, Eremia et al. noted an average of 74% hair reduction in all patients following three treatments with the laser.23 Patients with lighter skin showed above average clearance whereas those with darker skin showed below average results, the latter of which may be due to a lower fluence used for these patients. The authors attribute their success partly to a larger spot size which, at a given fluence, they believe would deliver more energy per pulse with less scatter and deeper penetration. Results of a study by Nouri et al., supported their postulation, concluding that a larger spot size is more effective for laser hair reduction.24 Three studies comparing various pulse durations of 2–20 ms found no significant differences in hair reduction.13,16,25,26
As with the ruby laser, there is a positive correlation between the number of treatments and the overall efficacy of treatment with the alexandrite laser, in one study reaching a 55% hair reduction in patients with skin types III–V.16,27 Also, when comparing three treatments using the laser with four treatments of electrolysis, it was found that the alexandrite laser was not only more effective (a 74% vs. 35% average hair reduction), but also less painful.28
In a meta-analysis of hair removal laser trials, the hair reduction for the diode, Nd:YAG, alexandrite, and ruby lasers were 57.5%, 42.3%, 54.7%, and 52.8%, respectively, at least 6 months after the last treatment of at least three sessions. The authors concluded that the diode laser is superior for lighter skin, while the alexandrite laser is the best choice for darker skin types.29
800 nm Diode Laser
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