Noninvasive computerized analysis of skin chromophores in vivo by reflectance spectroscopy.

Reflectance spectroscopy in an objective and accurate method for determining skin colour and has been widely used for measuring physiological variations in skin colour and for monitoring dermatological treatment modalities. Previous studies have used pigment indexes to describe changes in skin colour. Using a multiple regression method to calculate reflectance spectroscopic data, it has been possible to calculate the relative amounts of the different chromophores present in the skin. The technique was found reliable in in vitro tests and in experimentally induced variations in pigment content caused by venous congestion or ultraviolet (UV) light irradiation. In developing UV-induced erythema, the primary events seem to be venous dilatation followed by an increase in blood flow.