For example, the alexandrite laser – which has a relatively short wavelength (775 nanometers) – is effective on patients with lighter skin, although it is dangerous for patients with dark skin, while the neodymium-doped yttrium aluminum garnet laser – developed to have a longer wavelength (1064 nanometers) – works well on darker-skinned patients.
However, new lasers have been invented that work for different skin and hair combinations. For this reason, for many years laser hair removal was only possible for people with light skin and dark hair. If the skin and hair absorb the light at the same rate, the laser will not be able to “target” the hair.
Melanin under the skin – even if inactivated, will absorb rather than reflect light at the same rate as melanin of the same type in the hair. No single laser works on the complete range of skin and hair types (skin color is less relevant than melanin content), since the laser hair removal system works based upon a difference between skin and hair color in order for the hair to absorb the light without burning the skin. Figure 5: A cooling gel is applied just before the laser hair removal process begins.
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