Objective Assessment of Human Skin Reaction to Sun and UV-B

Abstract

Skin color and its changes in time are important in clinical dermatology. Experience shows, however, that the perceived skin color is influenced by many properties, such as (a) the skin surface (e. g.: humidity, oiliness, squamae), (b) the temporary blood perfusion of the skin, (c) structures in the corium and the corium/subcutis interface, (d) skin temperature [17], (e) previous sun exposures [6], and (f) the quite important ambient light conditions during examination. It has therefore been good practice in dermatology to judge skin color under standard natural illumination conditions, i. e., indirect sun light. It is interesting to note that the light energy spectrum of interest (100–3000 nm) has a maximum depth penetration in the visible and infrared (IR—A) range [9]. This nonlinear effect is, to a great extent, due to the energy absorption curve of water, which shows a steep minimum between 400 and 550 nm [14]. Moreover, because the penetration of light varies for different frequencies, the perceived color of deep lying structures can even be modified, a typical example is the “blue” aspect of the blue nevus.

This publication contains substantial results from the dissertation of P. Steiert