Skin whitening is the practice of using substances, mixtures, or physical treatments to lighten skin color. Skin whitening treatments work by reducing the content of melanin of the skin.
Melanin is the main substance responsible for the color of the skin. Melanin is class of dark polymers generated by the body through the process of melanogenesis. Among the melanin pigmenting the skin and hair, Two types can be distinguished based on its chemical composition and biological route of synthesis.the black/brown eumelanin and the red/yellow pheomelanin. The variation of skin color among individuals is mostly because of variation of the content of melanin in the skin. Skin with little or no melanin is almost white. Other factors influence skin color in a lesser degree, including the amount of blood in blood vessels (because of the color of blood), skin thickness and content of carotenoids in skin.
Skin whitening agents work by reducing the presence of melanin in the skin. To accomplish this, there are several possible mechanism of actions
- Inhibition of the activity of tyrosinase: The catalytic action of tyrosinase is inhibited (slowed or nearly stopped) by the skin whitening agent.
- Inhibition of the expression or activation of tyrosinase: The antimelanogenic agent causes that less tyrosinase is generated or that tyrosinase is not activated to its functional form.
- Scavenging of the intermediate products of melanin synthesis.
- Preventing the transfer of melanosomes to keratinocytes.
- Directly destroying existing melanin.
- Destroying melanocytes.