Reduction of regrowing hair shaft size and pigmentation after ruby and diode laser treatment

Optical evaluation of internal damage to human hair based on second near-infrared window polarization microscopy

OBJECTIVE

Hair beauty treatments glorify human life. As a side effect, there is a risk of deteriorating the health of the hair. Optically polarized microscopy has been used for many decades to evaluate hair conditions owing to its ease of use and low operating costs. However, the low biopermeability of light hinders the observation of detailed structures inside hair. The aim of this study is to establish an evaluation technique of internal damages in a hair by utilizing a near-infrared (NIR) light with a wavelength of 1000-1600 nm, called "second NIR window".

METHODS

We built a laser scanning transmission microscope system with an indium gallium arsenide detector, a 1064 nm laser source, and optical circular polarization to visualize the anisotropy characterization of keratin fibres in hair. Samples of Asian black hair before and after bleaching, after permanent-waving, after lithium bromide (LiBr) treatment, and after heating was observed. Some parameters reflecting intra-hair damage were quantitatively compared with the parameters in digitally recorded images with analytical developments.

RESULTS

The light transmittance of black hair was dramatically improved by utilizing the second NIR window. Numerical analysis of circular polarization in hair quantified the internal damage in chemically or thermally treated hair and found two different types of damage. The present method enabled quantitative evaluation of the condition changes in the cortex; for example, a decrease in circular polarizability by LiBr treatment and restoration by replacing the LiBr solution with water. In addition, black speckles were observed after the heat treatment. Longer heating and wetting times increased the appearance probability and size of the speckles. According to quantitative analyses, the emergence of black spots was independent of polarizability changes, indicating that they were not pores.

CONCLUSION

Circular polarization microscopy based on near-infrared optics in the second NIR window provides an effective evaluation method for quantifying intra-hair damage caused by cosmetic treatments. The present method provides noninvasive, easy, and inexpensive hair evaluation and has potential as a gold standard in hair care research/medical fields.

Polarization properties and Umov effect of human hair

This study delves into the polarization properties of various hair colors using several techniques, including polarization ray tracing, full Stokes, and Mueller matrix imaging. Our analysis involved studying hair in both indoor and outdoor settings under varying lighting conditions. Our results demonstrate a strong correlation between hair color and the degree of linear polarization. Specifically, light-colored hair, such as white and blond, exhibits high albedo and low DoLP. In contrast, dark hair, like black and brown hair, has low albedo and high DoLP. Our research also revealed that a single hair strand displays high diattenuation near specular reflections but high depolarization in areas with diffuse reflections. Additionally, we investigated the wavelength dependency of the polarization properties by comparing the Mueller matrix under illumination at 450 nm and 589 nm. Our investigation demonstrates the impact of hair shade and color on polarization properties and the Umov effect.

Contribution of Human Hair in Solar UV Transmission in Skin: Implications for Melanoma Development

Melanoma is the deadliest type of skin cancer with its prevalence on the rise. Recently, the melanocyte stem cells in hair follicles have been identified as the possible origin of melanoma upon exposure to ultraviolet radiation (UVR) through skin. It is hypothesized that colourless vellus hair (predominant in childhood) can serve as an alternative pathway in transmitting these ultraviolet (UV) photons to the stem cells. To investigate this, we have used the CRAIC microspectrophotometer to investigate the optical properties of 'vellus-like' hairs and terminal hairs of different colours using UV-VIS-NIR light sources. It was found that the average attenuation coefficient of 'vellus-like' hair is significantly lower than that of terminal hair in the UVA (p < 0.0001) and UVB (p < 0.001) wavelength ranges. Next, the optical properties of hairs are applied to simulations for examining their influence on UV transmission into the skin. The results show that the presence of vellus hair would increase the solar UV transmission to the melanocyte stem cell layer significantly. The findings explain why children are particularly vulnerable to sun exposure and the positive correlation found between the incidence of melanoma in adults' bodies and the number of vellus hairs in these areas.

Review of human hair optical properties in possible relation to melanoma development

Immigration and epidemiological studies provide evidence indicating the correlation of high ultraviolet exposure during childhood and increased risks of melanoma in later life. While the explanation of this phenomenon has not been found in the skin, a class of hair has been hypothesized to be involved in this process by transmitting sufficient ultraviolet rays along the hair shaft to possibly cause damage to the stem cells in the hair follicle, ultimately resulting in melanoma in later life. First, the anatomy of hair and its possible contribution to melanoma development, and the tissue optical properties are briefly introduced to provide the necessary background. This paper emphasizes on the review of the experimental studies of the optical properties of human hair, which include the sample preparation, measurement techniques, results, and statistical analysis. The Monte Carlo photon simulation of human hair is next outlined. Finally, current knowledge of the optical studies of hair is discussed in the light of their possible contribution to melanoma development; the necessary future work needed to support this hypothesis is suggested.

Laser treatment for female facial hirsutism: are quality-of-life benefits sustainable?

BACKGROUND

Facial hirsutism in women impairs quality of life (QoL). Laser hair removal (LHR) has been shown to confer significant improvements in QoL for up to 6 months after treatment, but the longer-term benefits have not been investigated.

AIM

To assess the sustainability of LHR benefits to the QoL of hirsute women up to 30 months after treatment.

METHODS

Hirsute women about to undergo National Health Service (NHS)-funded LHR in 2010-2012 (n = 142) completed proforma questionnaires quantifying the burden of hirsutism on their QoL. These included: the Dermatology Life Quality Index (DLQI) (assessing functional impact on QoL), the number of days spent removing hair per week and a 10-point scale assessing how much their condition bothered them (emotional burden on QoL). Postal questionnaires recorded QoL changes up to 30 months after LHR. Improvements in QoL scores for each woman were compared. Responses were then grouped into periods of 0-6, 6-12 and 12-30 months post-treatment, and the magnitude of change between these time groups was compared for each QoL measure.

RESULTS

In total, 63 women responded to the post-LHR questionnaire. QoL was severely affected, but improved with LHR. The number of days spent removing hair reverted to baseline at 12-30 months post-LHR, and a significant decline was seen in the magnitude of improvement in emotional burden on QoL over time (P = 0.04). However, no significant difference existed between improvements in DLQI scores (P = 0.12).

CONCLUSION

LHR supplies some functional QoL benefits up to 30 months post-treatment. Emotional benefits are less sustainable. Further LHR treatment is required to maintain QoL benefits.

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.

Optical properties of the medulla and the cortex of human scalp hair

An increasing number of applications, including non- or minimally invasive diagnostics and treatment as well as various cosmetic procedures, has resulted in a need to determine the optical properties of hair and its structures. We report on the measurement of the total attenuation coefficient of the cortex and the medulla of blond, gray, and Asian black human scalp hair at a 633-nm wavelength. Our results show that for blond and gray hair the total attenuation coefficient of the medulla is more than 200 times higher compared to that of the cortex. This difference is only 1.5 times for Asian black hair. Furthermore, we present the total attenuation coefficient of the cortex of blond, gray, light brown, and Asian black hair measured at wavelengths of 409, 532, 633, 800, and 1064 nm. The total attenuation coefficient consistently decreases with an increase in wavelength, as well as with a decrease in hair pigmentation. Additionally, we demonstrate the dependence of the total attenuation coefficient of the cortex and the medulla of Asian black hair on the polarization of incident light. A similar dependence is observed for the cortex of blond and gray hair but not for the medulla of these hair types.

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.

Pili bigemini complicating diode laser hair removal

After two diode laser treatments for hair removal, a 39-year-old woman was noted to have pili bigemini within the treated areas. It resolved after a third treatment. Pili bigemini, the appearance of two hairs coming from the same follicular opening, can be induced by intermediate doses of laser energy. It follows sublethal damage to the hair follicule apparatus.

[Histological changes elicited by hair removal lasers]

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. Unwanted hairs were treated with a ruby laser (ICN, Photon Ics, UK) at 10, 14, 18 J/cm(2) or an alexandrite laser (Cynosure, USA) at 11, 14, 17 J/cm(2). A 3 mm punch biopsy was taken immediately after each laser exposure and one month later. Specimens were stained for histological observations. They were observed using immunohistochemistry to Factor VIII related antigen and PCNA, and also by the TUNEL method. Immediately after the laser exposure, moderate follicular damage was observed following treatment with either laser. One month later, cystic formation of hair follicles and foreign body giant cells were observed in skin treated with either laser. The similar influence of each laser treatment resulted in similar histological changes. In this study, the histological changes following treatment with a ruby or an alexandrite laser at the same fluence were considered to be similar.

The effect of different spot sizes on the efficacy of hair removal using a long-pulsed diode laser

BACKGROUND

In the last years several lasers have proven their efficacy for hair removal. However, little is known about the efficacy of varying the spot size with those lasers.

OBJECTIVE

To evaluate the long-term efficacy of hair removal using a diode laser with different spot sizes.

METHODS

A long-pulsed diode laser (2 x 60 msec) was used. The spot size was 8 mm, 12 mm, or 14 mm. Twenty consenting volunteers were treated three times at regular intervals of 3 weeks. The ratio of the number of hairs in the treated area to an adjacent area left untreated (control) was referred to as regrowth.

RESULTS

One month after laser treatment, regrowth was 23% (8 mm), 12% (12 mm), and 13% (14 mm). After 3 months regrowth was 67% (8 mm), 54% (12 mm), and 55% (14 mm). Fifteen months after treatment 4 of 16 volunteers had a regrowth rate of less than 25%.

CONCLUSION

The results provide evidence for an effective and long-lasting growth delay of hairs using the long-pulsed diode laser. The use of large spot sizes improved the growth delay of hairs measured 1 month after treatment.

Hair removal by lasers and intense pulsed light sources

Laser and flash-lamp technology now offers the potential for rapid, safe, and effective treatment of unwanted hair. An ever-increasing number of published studies have confirmed the long-term efficacy of laser and flash-lamp treatment. The benefits of this technology have largely been limited to individuals with dark hair and relatively fair skin. The first studies using devices with a combination of longer wavelengths, longer pulse durations, and adequate epidermal cooling have shown that it is possible to safely and effectively treat individuals with darker skin types. The remaining challenge is to develop the means to eliminate light-colored hair as well. The increasing consumer demand for low-cost hair removal has driven the development of low-cost hair removal devices, such as small, pulsed flash lamps. The rapid pace of technologic advances and continued studies of hair follicle biology promise to improve this field over the years to come. In the future, small, low-cost laser-razors may replace all other means of hair removal.