Ruby laser-assisted hair removal: an ultrastructural evaluation of cutaneous damage

Dose-response of human follicles during laser-based hair removal: Ex vivo photoepilation model with classification system embracing morphological and histological features

OBJECTIVES

Photoepilation is a commonly used technology in home-use devices (HUDs) and in professional systems to remove unwanted body hair using pulses of laser or intense pulsed light (IPL). Albeit HUDs and professional systems operate at different fluences and treatment regimes, both demonstrate high hair reduction. The underlying mechanisms, however, remain unknown partly due to high divergence of the existing literature data. The objective of this study was to develop an ex vivo photoepilation model with a set of criteria evaluating response to light pulses; and to investigate dose-response behavior of hair follicles (HFs) subjected to a range of fluences.

METHODS

After ex vivo treatment (single pulse, 810 nm, 1.7-26.4 J/cm² , 4-64 ms pulse) human anagen HFs were isolated and maintained in culture for 7-10 days. Response to light was evaluated based on gross-morphology and histological examination (H&E and TUNEL stainings).

RESULTS

HFs treated ex vivo demonstrated a dose-dependent response to light with five distinct classes defined by macroscopic and microscopic criteria. Fluences below 13.2 J/cm² provoked catagen-like transition, higher fluences resulted in coagulation in HF compartments.

CONCLUSION

Observed changes in the HF organ culture model were reflected by clinical efficacy. The developed photoepilation model provides an easy and fast method to predict clinical efficacy and permanency of light-based hair removal devices. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Laser- and light-based hair removal: an update

A variety of laser technologies are now able to successfully remove unwanted hair. Successful removal is based on an understanding of laser physics and appropriate wavelengths, pulse durations and cooling of the skin. Although ruby lasers were among the first to be used, alexandrite, diode and neodymium-doped yttrium aluminium garnet (Nd:YAG) lasers, as well as a variety of broad-spectrum intense pulsed light sources, are currently more commonly used for the treatment of unwanted hair. Darker skin types are more difficult to treat but can also be treated. Complications can occur after laser hair removal but can be reduced through an understanding of the fundamentals of laser removal. These complications include the obvious, such as scarring and pigmentary changes, and the not so obvious, such as reticulate erythema and uveitis. Laser hair removal is now widely accepted as a successful approach to remove unwanted hair in both men and women. The future will involve office-based laser and light source hair removal, as well as a variety of laser and light-based home devices.

Histological hair removal study by ruby or alexandrite laser with comparative study on the effects of wavelength and fluence

BACKGROUND

Several different laser systems are currently used to remove unwanted hairs. In this study, we studied follicular changes following hair removal with ruby or alexandrite lasers at different fluences.

METHODS

Unwanted hairs were treated with a ruby laser (Chromos 694, ICN PhotonIcs, UK) at 10, 14 or 18 J/cm2 or with an alexandrite laser (LPIR, Cynosure, USA) at 11, 14 or 17 J/cm2. A 3 mm skin punch biopsy was taken immediately after each laser exposure and also 1 month later. Specimens were stained for histological observation. They were observed using immunohistochemistry with antibodies recognizing factor VIII related antigen or PCNA, and also by the TUNEL method. Similarly, electron microscopic observation was examined.

RESULTS

Immediately after the laser exposure, moderate follicular damage was observed following treatment with either type of laser. One month later, cystic formation of hair follicles and foreign body giant cells were observed in skin treated with either type of laser. A similar fluence with either laser treatment resulted in similar histological changes.

CONCLUSION

In this study, the histological changes following treatment with a ruby or an alexandrite laser at the same fluence are similar.

Mechanisms of Laser Hair Removal: Could Persistent Photoepilation Induce Vitiligo or Defects in Wound Repair?

BACKGROUND

Current laser hair removal modalities achieve a long-term but not persistent (irreversible) hair loss.

OBJECTIVE

This review highlights the mechanisms of the current laser hair removal technology and explores possible side effects.

METHODS

The literature is reviewed.

RESULTS

The hair shaft plays a key role in the mechanisms underlying current photoepilation procedures by acting as a vector for heat transfer. Together with inherent properties of the hair growth cycle and the anatomic specifics of the follicular stem cells located in the bulge, the crucial role of the hair shaft and its lack of complete destruction with present technology are also likely culprits for the nonpersistent nature of present laser hair removal. Future persistent photoepilation may be associated with vitiligo or vitiligolike changes. Disturbances in wound repair of previously lasered sites are less likely.

CONCLUSIONS

The currently available laser hair removal protocols are safe, not the least because they achieve long-term but not persistent epilation. The adverse effects of persistent laser hair removal technology possibly available in the future are potentially problematic.

A Pilot Study to Optimize Laser-Assisted Hair Removal Using Real-Time High-Speed Infrared Imaging

OBJECTIVE

The aim of this study was to investigate thermal effects on the skin surface during laser-assisted hair removal using real-time high-speed infrared imaging.

BACKGROUND DATA

Although hair laser removal (HLR) can be considered an inherently safe treatment, there may be approaches to optimise the benefit/risk ratio of this common therapeutic and cosmetic procedure.

METHODS

In this pilot study on three subjects, a ruby laser equipped with a cryogen spray cooling (CSC) system was used to investigate the effect of different CSC durations and delay times between CSC and the laser impulse. Skin surface temperature (SST) was assessed in real-time using a high-speed infrared camera (ThermaCam Phoenix) and a special image analysis software (analySIS Doku).

RESULTS

There was no substantial difference of SST between the use of CSC spurts of 10 and 20 msec (6.1 degrees C versus 5.7 degrees C). The use of single laser and cooling parameters revealed baseline SST of 31.7 degrees C, immediately after CSC (10 ms) SST of 6.5 degrees C, and after laser pulse SST of 47 degrees C. Using fluences of 10-20 J/cm(2), a marked difference in temperature was observed between the skin surface and hair (e.g., 26.7 degrees C versus 57.5 degrees C). SST of 62-64 degrees C was observed using fluences of 18-20 J/cm(2), resulting in adverse effects. A maximum SST of 59 degrees C was observed using a CSC spurt of 40 msec, whereas a maximum SST of 60 degrees C was recorded for 30, 20, and 10 msec. The use of CSC delay time of 600 msec revealed baseline SST of 34.6 degrees C, immediately after CSC (10 msec) SST of 5.2 degrees C, after 600 msec delay SST of 21.5 degrees C, and SST of 60 degrees C following the laser pulse. By contrast, 100 msec delay time revealed baseline SST of 34.8 degrees C, immediately after CSC (10 ms) SST of 7 degrees C, after 100 msec delay SST of 7.5 degrees C, and SST of 55.2 degrees C following the laser pulse.

CONCLUSION

Our preliminary data indicate that side effects of HLR can be avoided using CSC duration of 10 msec with a delay of about 200 msec. Short delay times between the CSC and laser pulse seem to result in lower post-irradiation SST and may therefore lead to less adverse effects. With regard to the fluence used in HLR, it is of importance that the maximum SST remains below 60 degrees C. Based on these preliminary results, real-time high-speed infrared imaging seems to be an interesting method to study the thermodynamics on skin surface during laser treatment.

The effects of laser-mediated hair removal on immunohistochemical staining properties of hair follicles

BACKGROUND

The mechanisms involved in laser-mediated hair removal remain unclear. One means of reducing hair growth is alteration of follicular stem cells.

OBJECTIVE

We sought to examine the effects of laser hair removal on the immunohistochemical staining properties of human hair follicles, including the putative stem cells of the bulge region.

METHODS

Treatment of unwanted axillary hair was performed on one side using an 800 nm-wavelength diode laser and on the other side using a 1064 nm-wavelength neodymium:yttrium-aluminum-garnet laser. Serial skin samples were obtained at baseline and various times after treatment and stained using immunohistochemical techniques.

RESULTS

Hair shafts were thermally altered, but the immunostaining properties of much of the follicle, including the bulge region, remained generally unchanged.

LIMITATIONS

This study only addressed the acute immunohistochemical changes found after a single treatment using specific laser parameters.

CONCLUSIONS

Laser-mediated hair removal does not appear to work by frank destruction of follicular stem cells. Other mechanisms including functional alteration of these cells may underlie the clinical efficacy of the procedure.

Ninety percent permanent hair reduction in transsexual patients

Transsexualism as a condition requires hair removal. Twenty-five male-to-female transsexual patients were included in this study on epilation using the Intense Pulsed Light Source (IPLS). Patients received a varying number of treatments, depending on their response. A mean hair clearance rate of 90% was achieved in the studied patients. The average number of treatments per patient was nine. A negative correlation was found between hair removal and the age of the patient. Hair removal was also found to be more effective when the patients had not used any needle epilation. No difference in hair removal was found between transsexual patients, who were hormonal, and those who were not. Follow-up lasted an average of 44 months. This study proved that the IPLS has the potential to be effective, permanent, and painless especially in younger patients who have not used any mechanical methods for epilation before photoepilation.

Patient satisfaction study of unwanted facial and body hair: 5 years experience with intense pulsed light

OBJECTIVE

This study was performed in order to evaluate patient satisfaction with epilation using an intense pulsed light source.

METHODS

Between 1995 and 2000, 416 patients consulted the authors' practice because of unwanted facial and body hair. A total of 309 patients received treatment with a non-coherent, filtered flashlamp intense pulsed light source. In February 2000, a questionnaire was mailed to each patient and 207 replies were obtained.

RESULTS

Overall, 45 (22%) of patients were very satisfied, 93 (45%) were satisfied and 69 (33%) remained unsatisfied with the outcome of light-assisted hair removal. The non-coherent, filtered flashlamp intense pulsed light source satisfactorily removed unwanted dark hair. Hair-free periods from weeks to years could be observed.

CONCLUSION

Hair removal by a non-coherent, filtered flashlamp intense pulsed light source is an effective and safe method for long-term epilation of unwanted hair. This technique offers a more reliable and practical solution than any other hair removal method, especially for patients with skin irritation and ingrown hair.

Long-pulsed ruby laser for permanent hair reduction: histological analysis after 3, 4 1/2, and 6 months

BACKGROUND AND OBJECTIVES

The histology of hair follicles in both animal and human skin treated with ruby lasers has been evaluated to a limited extent in previous studies. We have previously looked at such follicles up to 2 months after treatment. This study examines the longer-term effects at a microscopic level and attempts to further elucidate the mechanism of ruby laser hair reduction.

STUDY DESIGN/MATERIALS AND METHODS

Thirty-six patients underwent 1, 2, or 3 treatments of their axillary or bikini area skin with a 3 milliseconds ruby laser at 10, 20, 30, or 40 J/cm(2). Biopsies were taken 3, 4(1/2), or 6 months after the last treatment and examined histologically. Nine control biopsies were taken from comparable bikini areas of untreated patients and similarly evaluated histologically.

RESULTS

There was a significant increase in telogen compared to anagen follicles in treated skin, which was slightly increased by multiple compared to single treatments, but unaffected by different time intervals since the last treatment. There was also a significant increase in miniaturized compared to terminal hairs in treated compared to control skin, a finding that was further increased with higher energies used. Multiple treatments and time after treatment had a slight, but not statistically significant effect on follicle size.

CONCLUSIONS

Induction of telogen in terminal follicles followed by miniaturization appears to be the main mechanism of ruby laser hair reduction.

The long-term results of ruby laser depilation in a consecutive series of 346 patients

The goal of this study was to prospectively assess the long-term results of ruby laser depilation in 346 consecutive patients who underwent hair removal at 402 anatomical sites. The patients were treated using a ruby laser, with mean power ranging from 8.6 J to 15.7 J according to skin type. Results were assessed using two outcome measures-the percentage reduction in hair density and the hair-free interval. The median reduction in hair density was 55 percent (range, 0 to 100 percent) at a median time of 1 year after the last treatment session. The median hair-free interval was 8 weeks. Patients underwent a median number of four treatment sessions. Forty-three of the 346 patients were treated at more than one anatomical site. Of the sites treated, 75 percent reduction in hair density was achieved in 22 percent, 90 percent reduction was achieved in 2.2 percent, and complete depilation was achieved in only 0.7 percent. Darker colored hair was more effectively treated. Treatment efficacy was not affected by anatomical site, with the exception of the faces of male patients, which were found to be particularly resistant to treatment. There was a significant correlation between the number of treatments given and the outcome. The overall complication rate was 9.0 percent (36 of 402 sites) with respect to pigmentary changes and blistering, but varied according to Fitzpatrick skin type. The complication rate was highest in skin types V and VI (24.7 percent), with no complications in skin type I. Although a greater than 50 percent reduction in hair density was achieved in half of the 346 patients treated, complete depilation was achieved in only an extremely limited number of patients.

Laser hair removal: guidelines for management

Laser-assisted hair removal is the most efficient method of long-term hair removal currently available. Several hair removal systems have been shown to be effective in this setting: ruby laser (694nm), alexandrite laser (755nm), diode laser (800nm), intense pulsed light source (590 to 1200nm) and the neodymium:yttrium-aluminium-garnet (Nd:YAG) laser (1064nm), with or without the application of carbon suspension. The parameters used with each laser system vary considerably. All these lasers work on the principle of selective photothermolysis, with the melanin in the hair follicles as the chromophobe. Regardless of the type of laser used multiple treatments are necessary to achieve satisfactory results. Hair clearance, after repeated treatments, of 30 to 50% is generally reported 6 months after the last treatment. Patients with dark colored skin (Fitzpatrick IV and V) can be treated effectively with comparable morbidity to those with lighter colored skin. Although there is no obvious advantage of one laser system over another in terms of treatment outcome (except the Nd:YAG laser, which is found to be less efficacious, but more suited to patients with darker colored skin), laser parameters may be important when choosing the ideal laser for a patient. Adverse effects reported after laser-assisted hair removal include erythema and perifollicular edema, which are common, and crusting and vesiculation of treatment site, hypopigmentation and hyperpigmentation (depending on skin color and other factors). Most complications are generally temporary. The occurrence of hypopigmentation after laser irradiation is thought to be related to the suppression of melanogenesis in the epidermis (which is reversible), rather than the destruction of melanocytes. Methods to reduce the incidence of adverse effects include lightening of the skin and sun avoidance prior to laser treatment, cooling of the skin during treatment, and sun avoidance and protection after treatment. Proper patient selection and tailoring of the fluence used to the patient's skin type remain the most important factors in efficacious and well tolerated laser treatment. While it is generally believed that hair follicles are more responsive to treatment while they are in the growing (anagen) phase, conflicting results have also been reported. There is also no consensus on the most favorable treatment sites.