Substances, including different human tissues, react differently to specific wavelengths to accomplish desired effects.  For laser hair removal, the goal is to target the hair follicle without damaging surrounding tissue.  A chromophore is the substance that absorbs photons of light energy from a specific type of laser.  A substance may be a chromophore to a specific wavelength and not to another.  Different lasers with different wavelengths may target different chromophores to achieve desired results in hair removal.

Hair removal lasers use heat to destroy the hair follicle.  When the desired chromophores absorb the laser light, the light is converted to thermal energy in the form of heat. If a chromophore is heated beyond its capacity, the heat will be diffused into surrounding tissues.  It is the goal of physicians to reduce possible thermal damage (burns) by specifically targeting the melanin and not exceeding its heat capacity.  Newer lasers, if used properly, have extremely specific targets and are safe. 

The first FDA-cleared lasers were SoftLight™ Nd:YAG and ruby lasers.  Flashlamps were also used, although technically they are not lasers because they lack specificity.  The SoftLight™ actually used a carbon-based lotion applied after waxing as a chromophore.  This was found to be less effective than natural melanin found in the hair follicle.  Ruby lasers target natural melanin very well but, with a wavelength on 694 nm, these lasers are not very versatile for a variety of skin types and have become mostly obsolete. 

Diode lasers (810 nm) and Alexandrite lasers (755 nm) are still widely used today.  They target melanin specifically and can be used for a variety of skin types except for the darkest tones.  Lighter-colored, fine, and coarse hairs can be treated with these lasers.

The newest generation of hair removal lasers is long-pulse Nd:YAG at 1064 nm.  This wavelength allows physicians to safely treat dark and tanned individuals.  The addition of Nd:YAG lasers has broadened our ability to treat all skin types, but its limitation is in its ability to treat light-colored and very fine hairs.  The wide array of lasers available today has given physicians the necessary tools to safely and effectively treat unwanted hair.