Red, Blonde, Gray and White? Hairaway Canada provides the answer.

Semiconductor medical lasers are considered the most efficient sources of light available to achieve the cosmetic outcomes desired by those seeking to remove hair from various anatomical regions of the body.

According to the Wellman Labs of Photomedicine at Harvard Medical school, Medical lasers operate on the principles of selective photothermoloysis which "combine selective absorption of light energy by the MELANIN in hair follicles with suitable energy levels and providing cooling to the surrounding epidermal and dermal regions. "

The key and operative word and structure in the above sentence is Melanin.

Melanin is the pigment which provides the hair its color. It is also present in the eyes and hence the mandatory use of protective eyewear during the procedure and in a vast swath of humanity is what gives them their color; ranging from the peoples of the Mediterranean, to the Middle East, South America and Asia.

Advanced medical laser systems are designed to remove unwanted hair through this process of selective photothermolysis.  This involves the selective absorption of a very strong and intense  pulse of light at a continuous wavelenght by the hair follicles but NOT by the surrounding tissue. In medical laser hair removal the MOST important and dominant absorber of the energy generated by this strong and intense pulse of light a continuous wavelength is melanin.

In Red, Blonde, Gray and White colored hair, there is INSUFFICIENT melanin in the "hair follicle" and therefore the energy being generated by the medical laser cannot be effectively absorbed by the cell to cause the protein in the cell to become denatured and cause the elimination necessary to achieve the cosmetic outcomes desired.

Black and Dark Brown hair are ideal hair colors for medical laser hair removal. Red, Blonde and Gray and White as colored hairs simply do not have enough or any melanin in them and will not respond to the treatments provided.