Abstract
Although post-inflammatory pigmentation (PIH) is a common acquired skin disorder, however, its mechanism still remains unclear. In this paper, multimode optical spectroscopic techniques including diffuse reflectance spectroscopy, fluorescence spectroscopy and Raman spectroscopy have been used to probe the morphologic and biochemical changes associated with PIH. Both pigmented skin and the adjacent normal skin were measured for paired analysis. Distinctive spectral features were observed which may provide the potentials for identifying the mechanism of PIH. The diffuse reflectance spectrum was also converted into the CIE standard L*a*b* color system. The melanin and the hemoglobin content in the PIH were quantitatively derived from the diffusive reflectance spectrum using the Stamatas-Kollias algorithm. It was found that PIH always has a lower value in L* and more melanin and hemoglobin content which is consistent with clinical appearance of dark skin as perceived by the human eye.