Methods to overcome poor responses and challenges of laser hair removal in dark skin
Conventional and advance technologies are available for laser hair removal. Complete and permanent hair reduction is not yet possible by treatment with lasers. Ideal patient for any conventional laser hair removal treatment is one who has thick, dark terminal hair, light skin and normal hormonal status. Factors that contribute to variable outcomes in laser hair removal can be broadly divided into patient related ones and the technology related ones. Skin type, hair color, thickness and density, degree of tan, hormonal dysfunction etc., constitute the patient related factors. The wavelength, fluence, spot size and pulse duration of the laser system are the technology related factors. There are some patients who respond variably, unpredictably or poorly to laser hair removal despite ensuring that indication for treatment is appropriate with adequate parameters of the laser system. This article reviews various patient related and technology related factors which lead to variable-to-poor outcomes in laser hair removal; and various challenges and limitations of laser hair removal technology in patients with dark skin types.
Demand for laser hair removal has increased exponentially during the last decade. Traditional methods of hair removal such as threading, plucking and waxing have largely been replaced by interventions using laser and light sources as the latter methods are substantially superior in achieving long term hair reduction. Laser hair removal is said to be permanent when there is a stable decrease in the number of terminal hair for a period longer than the complete hair growth cycle at a given site after treatment. The target chromophore in laser hair reduction is melanin. Laser energy is absorbed by melanin in the hair follicle. Hair bulb, bulge and papilla are heated consequent to the absorption of laser energy. Energy is delivered to the target in lesser time than required for heat diffusion to the surrounding tissue which remains unaffected. Simultaneous cooling of the epidermis to protect it will achieve selective photothermolysis wherein there is selective absorption of wavelength by the chromophore. Evidence indicates that complete, total and persistent hair removal with lasers cannot be achieved. There is evidence which indicates that lasers induce complete but temporary hair loss, followed by partial, permanent hair reduction. Lasers produce significant delay in hair regrowth after treatment, which can last from weeks to months. After laser treatment, the terminal hairs are replaced by fine vellus hairs. Efficacy is improved when treatment is repeated.
Photothermal, photomechanical and photochemical mechanisms contribute to laser hair removal. Photothermal energy of laser causes a rise in temperature in hair bulb and bulge causing thermal destruction of hair follicle. Photomechanical energy initiates shock wave formation and photochemical energy is generated by free radicals.
Wavelengths in the range of 600–1200 nm produced by conventional systems such as ruby (694 nm), long-pulsed alexandrite (755 nm), long-pulsed diode (810 nm), long-pulsed Nd: YAG (1064 nm) and intense-pulsed light can achieve this. Radiofrequency also injures hair photothermally. Q-switched Nd: YAG laser (1064 nm), with or without the addition of a topical carbon suspension, destroys hair thermomechanically.
New techniques include low-fluence laser hair removal applied in motion with a high repetition rate to achieve progressive photothermolysis. Repeated and fast emission of pulses of low energy progressively heats the chromophore to temperatures of 45–50° over a period of time and safeguards the epidermis from overheating as opposed to a sudden rise in temperature to 65° in conventional systems. There are various factors related to patient and technology which could result in variable, unpredictable or poor responses to laser hair removal in spite of ensuring appropriate indications and adequate parameters of laser use. These are reviewed in this article.
Factors that contribute to variable outcomes in laser hair removal can be broadly divided into patient factors and technological factors .