The Science of Laser Hair Removal

Laser hair removal techniques are growing in popularity as a means for permanently or semi-permanently reducing unwanted hair on the body or face. This article will investigate the science behind laser hair removal in an attempt to give those considering the treatment some understanding of what they are contemplating.

Lasers function by targeting a chromophore, and in the case of laser hair removal, the chromophore is the melanin pigment found in hair follicles and skin. A hair’s germinative apparatus, largely responsible for its growth, is surrounded by melanin. When laser energy is absorbed by the chromaphoric melanin, a rapid rise in temperature results, and when sufficient, irreversible damage is caused to the germinative apparatus, resulting in cessation of that hair’s growth.

One barrier to the melanin in a hair absorbing sufficient energy to cause the destruction of the growth apparatus is the presence of melanin in the skin. Since the hair follicle resides sub-epidermally (below the skin),the laser must pass through the skin, 613 wig losing some of its energy to melanin in the epidermis. The darker the skin, the greater the concentration of melanin within it, and thus, the more energy is absorbed by the epidermal melanin and the more difficult it is to achieve good results, especially where the hair is lighter than, or only slightly darker than, the skin.

Hair removal laser treatment exploits the different cooling properties of the skin and the hair follicle. Since the skin has a far greater surface area to volume ratio and direct exposure to the air, cooling techniques, such as cooling with cryogen, cool air or a cooled crystal, either before, during or after the laser treatment. This increases the efficiency of the laser by allowing more energy from the laser pulse to reach the melanin that surrounds the hair growth apparatus in the hair follicle.

Multi-pulsed lasers work to further exploit this difference in the cooling properties of the skin and the hair follicle. These lasers break energy into a series of pulses separated my a gap of several milliseconds, allowing the skin to cool. The hair follicle, which is deeper under the surface, does not cool as quickly and is still hot when the next pulse is delivered. This both improves the efficacy of the treatment and prevents the skin from being damaged by the laser energy.


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