The optics of human skin: Aspects important for human health

Human health can be strongly influenced by exposure to solar radiation. Interactions relevant for health take place mainly in the skin. In this context the optics of human skin is of the utmost importance. Reflection, scattering and absorption are the optical properties affecting the nature of these interactions. By combining a bio-optical model of human skin with advanced radiative transfer theory, we simulated the transport of solar radiation through the skin. The calculated optical properties of the skin can then be combined with action spectra of various photobiological processes to calculate the efficiency spectra of these processes for different skin types. The main result of this study is that the interaction of solar radiation with skin is found to have considerable temporal variations due to the dynamic changes of the optical properties of the skin induced by solar radiation. In particular, variations in the brown colored melanin pigment are important for the optics of skin. The content of blood and proteins and the thicknesses of the skin layers may vary considerably and affect the efficiency of the photobiological processes.