Skin whitening cells causes the skin to naturally regenerate itself. Excess melanin comes to the surface and peels off in a few days. This is particularly useful in sensitive areas like the genitals where laser treatment could leave a scar. Efficacy of the treatment depends on the depth of the pigment. There is evidence to suggest that some types of skin-whitening products use active ingredients, such as mercurous chloride and hydroquinone, which can be harmful. Hydroquinone is not available without a prescription in Europe. It is only available when prescribed by a medical doctor (e.g. a general practitioner). This is also the
Pigment called metamerism. Averaged measurements of pigment samples will only yield approximations of their true appearance under a specific source of illumination. Computer display systems use a technique called chromatic adaptation transforms to emulate the correlated color temperature of illumination sources, and cannot perfectly reproduce the intricate spectral combinations originally seen. In many cases, the perceived color of a pigment falls outside of the gamut of computer displays and a method called gamut mapping is used to approximate the true appearance. Gamut mapping trades off any one of lightness, hue, or saturation accuracy to render the color on screen, depending on