Photoepilation: a growing trend in laser-assisted cosmetic dermatology

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Photoepilation: a growing trend in laser-assisted cosmetic dermatology
Accepted for publication August 12, 2007
Published Online: 31 Jan 2008
Keyvan Nouri, MD, Voraphol Vejjabhinanta, MD, Shalu S Patel, BS, & Anita Singh, MS
Department of Dermatology & Cutaneous Surgery, University of Miami Miller School of Medicine, Miami, Florida
Journal of Cosmetic Dermatology
Wiley InterScience

Keyvan Nouri, MD, Voraphol Vejjabhinanta, MD, Shalu S Patel, BS, & Anita Singh, MS
Department of Dermatology & Cutaneous Surgery, University of Miami Miller School of Medicine, Miami, Florida

Correspondence: Keyvan Nouri, MD, Professor of Dermatology & Otolaryngology, Director of Mohs, Dermatologic & Laser Surgery, Director of Surgical Training, Department of Dermatology & Cutaneous Surgery, University of Miami Miller School of Medicine, 2175 UMHC (UM Hospital & Clinics), 1475 NW. 12th Avenue Miami, FL 33136. E-mail: knouri@med.miami.edu

Copyright © 2008 Blackwell Publishing

KEYWORDS
hair reduction Ô hair removal Ô lasers Ô pulsed light Ô photoepilation

Abstract

Summary
Excess hair is an age-old condition plaguing both men and women alike, of all races. Conditions such as hirsutism or hypertrichosis, procedures that involve grafted donor sites, transsexual transformations from male to female, and genetics are all responsible for excess or unwanted hair. Previous options for people seeking to remove or lessen the presence of hair have either been painful or resulted in short-term hair removal. With the recent advent of laser technology, hair removal has been added to the many capabilities of the new generation nonablative lasers and light systems. Lasers are not yet a permanent solution for hair removal, but they are able to provide a safe, fast, and effective method of hair reduction.

DIGITAL OBJECT IDENTIFIER (DOI)
10.1111/j.1473-2165.2008.00363.x About DOI



Introduction


Photoepilation is becoming an increasingly popular trend in the arena of cosmetic dermatology, not to mention it being the prime focus of the med spa surge. According to the American Society for Aesthetic Plastic Surgery (ASAPS), 1 566 909 laser hair removal procedures were performed in 2005, compared with a still impressive 1 411 899 procedures just a year earlier.1,2 Only Botox injections precedes laser hair removal for both women and men according to the ASAPS's list of the top 5 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 proves to be an exception, with a 1.1% increase in women and about a 1.2% increase in men, for whom about 15% of the total laser hair removal procedures were performed. Most interestingly, 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 seen in patients with hypertrichosis or hirsutism, can be troubling both socially and psychologically.3 Past and present options for hair removal have included shaving, abrasives, epilation, depilatories, electrolysis, and, now most currently, lasers.4 All methods for hair removal have side-effects, but lasers have the advantage 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 U.S. Food and Drug Administration (FDA). They began allowing 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; thus, complete hair loss may be either temporary or permanent. Permanent hair loss is defined as a lack of regrowing hairs forever. Hair removal with lasers usually produces complete but temporary hair loss for 1 to 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. The theory describes how using specific parameters (wavelength, pulse duration, and fluence) can specifically destroy a specified cutaneous chromophore 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 to 1200 nm, to be effective.9 An 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 it also can 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 contact cooling, convective air cooling, or cryogen sprays. 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 precools 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 (5Ò100 ms) cryogen spurts 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 1064-nm Nd:YAG lasers use a variety of cooling mechanisms based on the laser used. Currently available is a chill tip cooling device, pulsed cryogen delivery to the skin, contact precooling, and air cooling. Finally, intense pulsed light (IPL) 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.10

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 (3Ò10 ms) and that of the hair follicle (10Ò100 ms).4,10 However, recent studies have sparked a reconsideration of the original theory suggesting a modification whereby the target is not destroyed by direct heating, but by diffusion from the pigmented area.10,11 This requires long pulses upwards of 100 ms known as superpulses to damage stem cells (thermal damage time). These superpulses would also damage other crucial targets, such as stem cells, which may be another factor for permanent hair reduction.9

In darker skin, using longer wavelength such as Nd:YAG laser (1064 nm) can limit complications from the procedure. However, lighter skin individuals, who have less eumelanin in the hair shaft, need shorter wavelength lasers such as the long pulsed ruby (694 nm) or the long-pulsed alexandrite laser (755 nm) to increase efficacy. In some cases, it has been reported that laser treatment actually induced hair growth, particularly on the face and neck. For example, in one study, this was noted in young females of Mediterranean and Middle Eastern descent and with darker skin types (III or IV).12 The induction of hair growth occurred regardless of the fluency or type of laser used, whether IPL or long-pulsed alexandrite laser. Because neogenesis of hair follicles after birth does not occur, it is likely that the reasoning behind laser-induced hair growth is that local vellus hair follicles transform into terminal pigmented hair follicles.12

In addition, people with certain skin conditions such as vitiligo and psoriasis should avoid laser hair removal in those areas, as it may koebnerize.

The current market for laser hair reduction is growing so rapidly that the FDA cannot even maintain an up-to-date listing of all approved laser devices. The lasers in this market 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 (800Ò810 nm), and the long-pulsed Nd:YAG laser (1064 nm). Additionally, the IPL system (500Ò1200 nm) is currently approved as a safe and effective method for hair reduction.



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. published the results of their study of this laser system and showed very good results for long-term hair reduction using higher fluences.14 The average follow-up time after the last treatment was about 8 months. They found that those study patients who had received treatment with a higher mean fluence of about 46 J/cm2 had sparse regrowth, whereas those who had received a lower mean fluence of about 39 J/cm2 had moderate regrowth. Although an increase in fluence may contribute to overall efficacy, it also increases the frequency of side-effects.13 These may include post-treatment erythema, crusting, blistering, hypopigmentation, hyperpigmentation, and even scarring. These side-effects, especially pigmentary alteration and scarring, were much more common in darker skin, specifically skin types IV to VI, than in lighter treated skin.15 This is because the short wavelength allows for greater absorbance of the laser light by epidermal melanin, which is more abundant in darker skin types. Consequently, studies with this laser primarily involve lighter skin patients.15 It should be noted also that using a ruby laser with a pulse duration of 1 ms (as opposed to 20 ms) has proven to cause greater epidermal damage in patients with darker skin.16,17

Overall, most studies performed using this laser have concluded that the 694-nm ruby laser is a safe and effective method for nonpermanent hair reduction.13Ò15,18,19 When comparing three treatments using the ruby laser with three treatments of either waxing or electrolysis, it was found that the laser provided a 38% to 49% hair reduction, whereas the alternatives provided no significant change.16,18 Increasing the number of treatments appeared to correlate with a decrease in overall hair counts.16,18Ò21 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 because they have the ideal combination of profuse deposits of melanin in the hair and lesser amounts in the epidermis. Fewer side-effects are associated with this population of patients as well.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, thereby theoretically making adverse side-effects less of a concern for darker skin patients compared with the ruby laser. However, studies indicate that blistering, hypopigmentation and hyperpigmentation occurred in darker skin types, with some cases more severe than others.13,15 Results have consistently shown good clearance rates for hair reduction.

Lloyd and Mirkov reported a 78% clearance of hair 1 years following final treatment of their patients.22 Similarly, Eremia et al. noted an average 74% hair reduction in all patients following three treatments with the laser.23 Despite the longer wavelength, patients with lighter skin showed above average clearance, whereas those with darker skin had below average results. The results for the darker skin patients may have been due to a lower fluence used for these skin types. 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 compared with a smaller spot size. Results of a study by Nouri et al. support the authors' postulation, concluding that a larger spot size is more effective for laser hair reduction.24 Three studies comparing various pulse durations of 2 to 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 IIIÒV.16,27 In addition, 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 it was also less painful.28



800-nm diode laser


The 800-nm diode laser is similar to the 755-nm alexandrite and has become more popular along with the Nd:YAG laser for treating patients with darker skin types. Both the diode laser and the alexandrite laser produce light in the middle of the spectrum (infrared) and are well absorbed by follicular melanin. Bouzari et al. compared the alexandrite, diode, and Nd:YAG and found that the alexandrite and diode lasers have similar efficacy.29 Furthermore, Eremia et al. compared results after 1 year using the alexandrite and diode lasers and concluded that both were excellent (85% and 84%, respectively) for long-term hair reduction with no statistical difference between the two laser systems.16,30 The authors partially attribute the success of their results to the use of relatively high fluences that they were able to use by carefully selecting patients that were untanned. Tanning increases the chance of complications such as blistering, necrosis of the skin, and pigmentary alterations, and it also lowers the effectiveness of the laser. Another study also found similar results between three treatments of either the alexandrite laser or diode laser. However, in this study, the hair reduction was about 37% to 46% for the two lasers. Furthermore, the results showed that the diode laser was more painful and had greater side-effects, particularly hyperpigmentation and blistering, compared with the alexandrite laser.16,31

A study comparing various spot sizes (8, 10, and 14 mm) found that after three treatments and at a 3-month follow-up, there was not a significant difference in hair reduction.16,32 However, as with the ruby laser and the alexandrite laser, two treatments with the diode laser resulted in a greater hair reduction (35Ò53%) than one treatment (28Ò33%) after an average 2-month follow-up. Also in this study, it was concluded that the diode laser provided a significant hair reduction as compared with shaving (13Ò36% vs. Ò7%).16,33

A recent study testing the efficacy of a newer 810-nm diode laser on patients with Fitzpatrick skin types II to IV found histological and clinical evidence of hair reduction (70%) at 6 months of follow-up.34



1064-nm Nd:YAG laser


The 1064-nm Nd:YAG has the longest wavelength and deepest penetration of the aforementioned laser systems available. Although it is not very well absorbed by melanin when compared with shorter wavelength, it is sufficient to achieve selective photothermolysis.35 What it lacks in absorption, it redeems in penetration. The Nd:YAG is able to penetrate the skin 5 to 7 mm where most of the target structures lay. Furthermore, the combination of a low melanin absorption and deep penetration turns out to be advantageous to the melanin-containing epidermis, which is thus spared. These parameters make this system the safest choice for tan or darker skinned patients.9,35 Although this laser may be the safest way to treat darker skin types, or any skin type for that matter, it is not necessarily the most effective. Bouzari et al. compared hair reduction caused by the long-pulsed Nd:YAG, alexandrite, and diode lasers and found that after 3 months, the Nd:YAG was the least effective of the three.29 An interesting aspect of their study was that they reported the best results in five patients who underwent combination laser therapy that included treatment with all three systems. They hypothesize that using a variety of wavelengths, they are able to damage hairs at different ranges in the skin: longer wavelengths would damage the deeper hairs and the shorter wavelengths would damage the more superficial hairs. This is similar to laser tattoo removal which incorporates a combination of lasers to remove the multitude of pigments found in a given tattoo.

A study determining the safety and efficacy of the long-pulsed Nd:YAG laser for all skin types found that the treatments were more successful (46Ò53% depending on location) in darker skin patients (types VÒVI). At 6 months, patients with skin types I to II obtained a 41% to 43% hair reduction, depending on location, whereas patients with skin types III to IV obtained a 44% to 48% hair reduction.36 Another study comparing fluence levels found similar hair reductions for levels of 50, 80, and 100 J/cm2 (29%, 29% and 27%, respectively) in patients with skin types II to IV.37



IPL


The IPL system is not technically a laser, but has recently entered the hair removal arena as a competent contender. In fact, they have been used for virtually all of the same indications as laser systems. Unlike lasers which emit monochromatic light, IPL systems have flashlamps that produce noncoherent, polychromatic light in the spectrum of 515 to 1200 nm.38 IPL systems work very similarly to lasers. Their mechanism of action is based on the principle of selective photothermolysis. IPL systems, unlike lasers, use a polychromatic light that can be used to simultaneously treat both pigmented and vascular lesions. Polychromatic light irradiates multiple chromophores with both major and minor absorption peaks, allowing for greater selective energy absorption.6

Results using this system have been comparable to the other lasers mentioned in this article. Like lasers, dark-haired patients responded better to IPL treatment than did blonde or gray-haired patients who also required more treatment sessions.39 IPL is not capable of achieving permanent hair removal, but long-term hair reduction with few side-effects is possible.40 Schroeter et al. recently concluded their study following the long-term effects of this laser on hirsute women. They compiled very good results of 87% mean hair reduction after an average of 27.4 months and eight treatments. Positive results correlated with the number of given treatments. Side-effects are mild and transient with this system.41

A randomized controlled trial compared the effect of one treatment of IPL with one treatment using the long-pulsed Nd:YAG laser in patients with skin types IV to VI and found at a 6-week follow-up that there was no significant difference in hair reduction. However, the IPL treatment resulted in postinflammatory pigmentation (45%), whereas the other did not.16,42 A nonrandomized controlled trial which compared three treatments of IPL with three treatments using a ruby laser found that in skin types II to IV, 94% of patients obtained an average 49% hair reduction using the IPL system at a 6-month follow-up. With the ruby laser, 55% of patients obtained an average 21% hair reduction at that time.16,43



Radiofrequency combinations


Radiofrequency (RF) devices have been combined with both IPL and diode laser to provide optimal hair removal treatments to a wider range of skin types. The combinations are considered safe for patients with darker skin types because the radiofrequency energy is not absorbed by melanin in the epidermis. This technology, termed electro-optical synergy, or ELOS, has a dual mechanism of heating the hair follicle with electrical energy (i.e., radiofrequency) and heating the hair shaft with optical energy.

The newest evolution in photoepilation involves removing nonpigmented hairs such as "peach fuzz", which the previous lasers fail to remove. A combination of RF and lasers has been used for white or blonde hair, but with low efficacy. In recent studies, the combined use of RF and optical energy has been investigated and shown potential benefits, although various mechanisms have been proposed to explain its effect.44Ò47 Some claims of widespread safety have been made because RF energy is not readily absorbed by the melanin abundantly found in the epidermis of darker skin types, theoretically sparing it from damage. A low efficacy of this new technology has been reported so far. Results have indicated that though there has been some success; the majority of subjects achieved less than 50% hair reduction after 3 months.45 In two other studies, 18-month follow-ups indicated a 48% average clearance46 and a 75% average clearance.47 Because this is a relatively new technology, more studies are clearly necessary to provide reliable results for those with nonpigmented hair or with darker skin types.



Other removal methods for nonpigmented hair
Meladine, a topical melanin chromophore, has been studied in Europe with interesting results. The liposome solution dye, which is sprayed on, is selectively absorbed by the hair follicle and not the skin. This gives the follicles a temporary boost of melanin to optimize laser hair removal treatments. Clinical studies in Europe have shown vast permanent hair reduction in patients who used Meladine prior to treatment. However, other studies have found Meladine to only offer a delay of hair growth as opposed to permanent hair reduction.6

Photodynamic therapy may be an effective option for those with nonpigmented or light-colored hair. Because of the lack or diminished amount of a natural chromophore in the hair follicle, a topical photosensitizer, 5-aminolevulinic acid (5-ALA), is used. Light exposure activates 5-ALA, which subsequently creates reactive oxygen and allows for destruction of the hair follicle.6



Laser treatment approach


When interviewing a patient who is considering laser hair removal, obtaining a patient history is very important. It is imperative to obtain the patient's expectations, what medications they are currently on, their history of hypertrophic scars or keloids, whether or not there is a local infection in the area, whether or not they have tried other hair removal strategies in the past, their endocrine status such as diabetes, polycystic ovarian syndrome, or hyperandrogen status, and the amount of sun exposure they have recently had. In addition, multiple sessions must be mentioned to patients. Physical examination is also very crucial and should be performed to evaluate the patient's skin color and skin condition, hair color, hair diameter, and hair density and also to exclude other systemic diseases.

Once a patient is determined as a good candidate for hair removal, then certain preoperative steps 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 area that they would like treated. However, they can shave. Depilatory creams should be avoided in order to prevent irritation or contact dermatitis. It has been shown that greater hair loss occurs at shaven rather than epilated sites according to remaining of the hair shaft for laser absorption. In addition, the treatment area should not be exposed to the sun.6

The day prior to the laser treatment, the patient should be instructed to shave on the treatment site. Some physicians also advise patients to start the use of prophylactic antiviral agents, if it is necessary. On the day of treatment, the area must be cleaned and free of make-up. If necessary, a topical anesthetic is applied 1 to 2 h before the procedure.6

Postoperatively, ice packs can be used to reduce pain and minimize edema. Rarely are analgesics needed. Mild topical steroid creams may be given to the patient to decrease posttreatment erythema and edema. If any epidermal injury occurs during the procedure, a topical antibiotic/white petrolatum can be given to the patient; however, risk of allergic contact dermatitis or folliculitis should be of concern. The patient should be advised to use sun block and to avoid direct sun exposure before and after treatment.6



Contraindications


Patients with active cutaneous infections should not be treated until the area is clear. 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 that are on hormonal therapy should be advised of limitations of hair removal treatment. Patients with vitiligo and psoriasis should be warned of the risk of koebnerization following laser surgery. Finally, patients on minoxidil or with spouses on this medication should be warned that this medication may decrease the efficacy of laser treatment.6



Adverse events


Patients should be warned before the laser procedure that they may experience some discomfort during and after the procedure, and there may be perifollicular erythema and edema to the area afterwards. Other adverse events include herpes simplex outbreaks in patients with a previous history of outbreaks, folliculitis in patients who sweat excessively or enjoy swimming, transient and permanent pigmentary changes, temporary or permanent leucotrichia, loss of freckles or lightening of tattoos, livedo reticularis, intense pruritus, and urticaria.6



Conclusion


Currently, the FDA has not approved any laser for marketing as a permanent hair removal option, although it has granted approval for some manufacturers to claim permanent hair reduction based on safety and efficacy.

In general, the ruby laser can be used for skin types I and II, although the alexandrite laser and the diode laser may be considered safer. The Nd:YAG laser is ideal for tanned skin and skin types IV, V, and VI, but has a lower efficacy in lighter skin types. Current studies are beginning to investigate the safety and efficacy of specific and newer lasers for various skin types. Combinations of different wavelengths and exogenous chromophore applications are interesting topics to increase the efficacy of laser treatment. This is important because as the popularity of photoepilation continues to grow, so will the population of patients interested in this procedure. The challenge ahead lies in gathering strong data from standardized, long-term studies so that optimal parameters can be established for the ultimate goal of permanent hair removal.




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