Dyeing Regions of Oxidative Hair Dyes in Human Hair Investigated by Nanoscale Secondary Ion Mass Spectrometry

The study investigated the distribution of colored chromophores formed by oxidative hair dyes in human hair using deuterium-labeled dyes and nanoscale secondary ion mass spectrometry (NanoSIMS). The results showed that these chromophores were intensely localized in melanin granules, indicating that melanin granules are crucial dyeing regions for oxidative hair coloring. This finding was supported by the detection of deuterium ions in particulate regions identified as melanin granules. The study demonstrated that NanoSIMS is a powerful tool for examining the interactions of cosmetic ingredients with the fine structure of human hair.