Hair Removal with the Long-Pulse Alexandrite Laser (2024)

Abstract

Removal or reduction of unwanted and dark-colored hair is important to personal grooming and attractiveness, particularly in Western culture. Various methods have been employed for this purpose, including shaving, waxing, clipping, plucking, mechanical depilation, radiation, electrolysis, surgical excision, and the use of chemical agents and drugs.^1–3

Currently, 1 million women in the United States undergo electrolysis annually, at a total cost of approximately $1 billion, while an additional 80 million women spend a total of $500 million on depilatory products.⁴

Principles of Laser Hair Removal

Laser depilation has provided an alternative, clinically superior means of permanent hair removal since Goldman et al⁵ first described ruby laser injury to pigmented hair follicles in 1963. The efficacy of this technique is altered and affected by several variables depending mainly on the laser light itself, and hair follicle and skin characteristics.

Laser hair removal is generally based on a physical process called “selective photothermolysis,” which was first described by Anderson et al.⁶ This process is defined as the absorption of laser energy specifically by the hair follicle rather than by any other possible target on or within the skin surface. The “melanin” contained by the hair follicle is the target “chromophore.”⁷ Both the physical and chemical effects created by the laser's thermal energy accomplish the destruction of the target.

The hair follicle resides in the dermis of the skin and consists of 3 distinct parts: the bulb, the isthmus, and the infundibulum. Melanocytes are located in the bulb and bulge of the hair follicle, which are approximately 4 mm below the skin surface. To effect hair removal, the laser energy must target the skin layer housing the bulb and bulge. This is achieved by altering the laser wavelength and spot size. Longer wavelengths penetrate more deeply in the dermis but are less absorbed by melanin. The larger the spot size, the deeper the laser light penetrates.

The growth cycle of the hair follicle is another important factor affecting the results. A complete cycle consists of 3 phases: anagen, catagen, and telogen. The period in which the hair is most susceptible to laser light is the anagen, or active growth phase.^8,9 The duration of the cycle varies on different parts of the body; consequently, more than one laser session is usually needed because follicles on different parts of the body are in different phases of growth.

Currently, lasers with a variety of wavelengths are used for hair removal, ranging from the 695-nm ruby laser at the short end to the 1064-nm Nd:YAG laser at the long end.¹⁰ While shorter wavelengths are ineffective in achieving the desired long-term hair removal, longer wavelengths are too close to the light absorption rates of oxyhemoglobin and melanin to be fully effective. The alexandrite laser, which is almost in the middle of this spectrum with its 755-nm wavelength, represents an ideal choice.

The energy of the laser light is defined by the number of photons delivered to the target and is measured in joules (J). The power of laser a device defined by the amount of energy delivered over time and is measured in watts. Fluence is the energy applied on unit area (J/cm²). Spot size is defined by the diameter of the laser beam; large spots allow deliverance of more effective fluences in the dermis.¹¹

In order for laser treatments to be safe, the surrounding tissue must be preserved while the laser energy destroys the hair follicle. This is achieved through application of the principle of thermal relaxation time (TRT). This term refers to the cooling duration of the target; selective thermal damage is accomplished when the energy delivered is longer than the TRT of the adjacent structures but shorter than the TRT of the hair follicle, so that the target is not allowed to cool and consequently the hair follicle is damaged.^11,12 While the TRT of epidermis had been measured as 3 ms, it takes almost 40 to 100 ms for the hair follicle to cool. In addition to this principle, cooling devices can be used on the skin. Such devices both protect the skin from possible thermal damage and reduce pain for the patient, thus enabling the operator to deliver more energy safely.

Patients and Method

Our study is based on the retrospective data analysis and evaluation of 322 patients, all of whom received alexandrite laser hair removal in more than 3 sessions between January 2000 and December 2002.

We used a long-pulse alexandrite laser that can deliver a laser beam at a constant spot size (18 mm) and 3-ms pulse width, operating at 755 nm (Candela Gentlelease Plus, Candela Corp, Wayland, MA).

We performed the procedure for 2218 sessions on 595 different body parts of 19 male, 264 female, and 39 transsexual patients. The skin types of the patients were rated according to the Fitzpatrick classification.¹³ A total of 188 patients (60.5%) were Fitzpatrick skin type III, 81 (25.1%) were skin type II, and 40 (12.4%) were type IV. Four patients were skin type I and 5 were skin type V (Figure 1). The body areas treated included the whole face, upper lip, chin, sideburns, mustache, axilla, trunk, arms, legs, and bikini area. More than 88% of our patients received treatment to more than one body part.

Prior to treatment, all patients were evaluated by a physician and informed of the mechanism, efficacy, and possible side effects of laser hair removal. The area to be depilated was marked with a highlighter pen according to the desire of the patient and the physician's suggestions. All patients were pretested before treatment to determine the level of energy that could be delivered without any side effects.

Patients with any existing systemic disease or who had a history of sun sensitivity were not treated. Those who underwent less than 3 sessions were excluded from the study. Patients with very light hair color were treated but not included in the study.

Patients were also asked about the use of any drugs known to cause photosensitivity; alternative methods of hair removal were offered to patients who answered positively.

Before each session, the same physician evaluated all patients and their hair reduction rates were noted. If requested by the patient, topical anesthetic EMLA 5% cream (AstraZeneca LP, Wilmington, DE) was applied 1 hour prior to laser therapy and the area was wrapped with an occlusive dressing with Tegaderm (3M, St. Paul, MN). During the sessions, pain relief was achieved by a dynamic cooling cryogen spray (Candela Gentlelease Plus, Candela Corp, Wayland, MA) and an additional active air-cooling system. Use of these 2 systems not only increased patient comfort but also protected the surrounding tissue.¹⁷

Sessions were repeated at 4- to 10-week intervals. Facial treatments were repeated every 4 or 6 weeks; the intervals between treatments were gradually increased. Body or extremity treatments were delivered at 6-, 8-, or 10-week intervals. After each session, a wet dressing with 2% boric acid was applied for 5 to 10 minutes. This was an effective antiseptic and also resolved any pain and burning experienced by the patient. Subsequently, dexpanthenol cream was applied to the face, lotion to the body, and chlorhexidine HCl to body areas susceptible to infection. Finally, all patients were instructed to use sun block, SPF 40-60, during the treatment period.

Patients were checked at the end of the second week after each session, and any missed or remaining hair follicles were destroyed with retouch shots.

Results

The overall hair reduction rate for all patients, independent of skin type, was estimated as 80.8% (Figures 2 and 3). The breakdown of this result according to skin type showed mean reductions of 82% for Fitzpatrick type II patients, 80.5% for Fitzpatrick type III, patients and 80% for Fitzpatrick type IV patients. Results for patients in the Fitzpatrick types I and V were not recorded because the number of patients in these groups was too small to be statistically significant.

Hypopigmentation developed in 2 patients, while hyperpigmentation developed in 8 patients. One case of permanent hypopigmentation was caused by applying double shots to the same area in accordance with the patient's request. The second case was likely a side effect of the laser treatment and resolved completely after 6 months.^18–20

As reported before, hyperpigmentation is a more common complication of laser therapy and frequently heals spontaneously. In our series, all hyperpigmentation cases resolved in 1 to 3 weeks. If the change in skin color persisted for more than 2 weeks, hydroquinone-based topical agents were applied. After identical crescent-shaped hyperpigmentation occurred in 2 patients, we examined the laser and found a failure in the lens; the machine was subsequently checked daily. No instances of scarring, crusting, blistering, or infection were noted. Almost all patients developed mild hyperemia and perifollicular edema following the treatment, which resolved after several hours; these effects were regarded as a sign of effective therapy. No complications were seen in one pregnant patient who underwent hair removal.

Discussion

When we reviewed the literature on laser hair removal, we realized that our series contains the largest reported number of patients evaluated and largest reported number of sessions applied. Because the mechanism of action, physical and chemical effects of laser energy, and statistical results of hair follicle removal had been previously published, we sought in this paper to share our practical experience and method of applying the technique, rather than to again demonstrate its effectiveness.^14–16

In our view, a mean 80.8% hair reduction rate can be considered excellent. Two factors contributed to this result. First, and perhaps most important, was patient compliance with the treatment regimen, which allowed us to apply more than 1 or 2 treatment sessions. After each, we noticed a mean reduction of 15% to 35% in the total amount of hair, depending on the area treated and the patient's skin type and hair color. Hair reduction rates increased in every following session, which improved patient motivation. Careful pretreatment patient education also contributed to compliance with the treatment regimen, as patients were informed about the hair growth cycle and advised that effective therapy can take more than 1 or 2 sessions. In short, the efforts made to educate patients before treatment began were a key factor in achieving a successful result.

Another key to successful results is a careful patient examination and skin typing prior to treatment. In our practice, accurate pretesting shots were made and evaluated and the highest effective fluence for the therapy was determined. Testing shots were evaluated approximately 72 hours later. As emphasized before, we called all patients in for retouch sessions 2 weeks after each main session was performed. The 2-week period provided sufficient time for damaged follicles to fall out, and any follicles missed in the treatment session were treated in the retouch session.

Some patients may not be satisfied with 80% hair reduction. Almost all male patients who present with pseudofolliculitis barbae, or dense hair growth on unwanted parts of the face, such as ears or periorbital areas, are satisfied with an 80% reduction. Although women generally desire complete hair removal, most are pleased with permanent loss of almost 80% of hair in a few sessions of such a painless and easy treatment method. Moreover, they understand that better results could be easily achieved through additional sessions.

One point worthy of note is the disparity in the hair reduction rate for different body parts in the same patient. Although different areas may receive the same fluence, spot size, and number of sessions, because of differences in skin thickness and the hair growth cycle for different parts of the body, results will vary. Patients should be informed of such disparities as part of the pretreatment patient education process.

For patients with Fitzpatrick type II or IV skin types, we frequently delivered fluences of 16 J and 18 J, and sometimes even 20 J, without any adverse side effects. We preferred to treat the Fitzpatrick type II group with 20 J. If we noticed that the patient was suntanned between the sessions, we widened the interval by an additional month and decreased the fluence.

Our experience in using laser hair removal for pseudofolliculitis barbae of patients with coiled hair was quite positive. Even though several other treatment modalities, such as various shaving devices, electrolysis, and surgery often are recommended for these patients, we want to emphasize that laser therapy is the most efficacious treatment and should be the chosen therapy.^21,22

Conclusion

Hair removal through treatment with the long-pulse alexandrite laser is effective in meeting the expectations of the patients who desire permanent hair reduction. When compared with other techniques, this method is faster and provides greater patient comfort. For optimal results, we recommend that physicians provide extensive patient education and follow the treatment guidelines summarized above.

References

Author notes

This study was presented as a poster at the 6th Panhellenic Plastic, Reconstructive and Aesthetic Surgery Congress in Athens, Greece, October 1–5, 2003.

© 2005 The American Society for Aesthetic Plastic Surgery, Inc.