Background/purpose: Clinical experience has shown that red haired, fair-skinned people have an increased frequency of skin cancer and in addition a relatively high content of pheomelanin and low content of eumelanin in their skin. Of these, eumelanin is presumed photoprotective, and pheomelanin phototoxic. Thus, a fast, easy, and non-invasive method for determining skin content of eumelanin and pheomelanin was sought.
Methods: Skin reflectance measurements using a UV-Optimize apparatus were performed before taking suction blisters of the same skin area. Each skin sample was freeze dried and submitted to alkaline hydrogen peroxide degradation. Two eumelanin degradation compounds:Pyrrole-2,3-dicarboxylic acid (PDCA) and pyrrole-2,3,5-tricarboxylic acid (PTCA), and two pheomelanin degradation compounds: Thiazole-4,5-dicarboxylic acid (TDCA) and 1,3-thiazole-2,4,5-tricarboxylic acid (TTCA) were determined in a single chromatographic analysis. Each degradation compound was correlated to reflectance measurements of red (660 nm), green (555 nm), and blue (488 nm) light and additionally correlated to the pigmentation % and redness % given by UV-Optimize.
Results: Neither of the investigated parameters were significantly correlated to either PDCA or TTCA. Contrarily, a highly significant correlation was found for the eumelanin marker, PTCA (r2=0.79, P<0.0001). The pheomelanin marker, TDCA, was likewise found to be significantly correlated (r2=0.43, P<0.0001).
Conclusion: Based on the coefficients of determination it was concluded that in vivo spectrophotometric reflectance measurements of human skin were highly useful for determining the eumelanin content of skin and to classify the pheomelanin content of skin non-invasively. This may be used individually and in population-based studies.