Non-Invasive Estimation of Skin Thickness by near Infrared Diffuse Reflection Spectroscopy—Separate Determination of Epidermis and Dermis Thickness:

This paper reports a non-invasive method for estimating skin thickness by using near infrared diffuse reflectance (NIR-DR) spectroscopy. Skin thickness is an important skin property in cosmetology, dermatology and pharmaceutical science. It varies significantly between the face and other body parts and changes with age and environment factors. Differences in skin thickness reflect the structural conditions of the epidermis and dermis. However, current methods for measuring skin thickness are complex and require cumbersome equipment. Therefore, we herein propose a NIR-DR and partial least squares (PLS) regression method for non-destructive skin thickness estimation. NIR-DR spectra were measured for UV-irradiated and non-irradiated skin on the backs of hairless mice and denuded back skin. Skin thickness increased gradually with the amount of UV irradiation, while changing little with physiological age. To obtain reference data, optical microscope measurements were carried out for denuded skin and total thic...