Chelation of Monoazo Dyes in Human Hair Keratin Fibers Using Environmentally Benign Metal Ions.

The coloration of human hair keratin fibers has long involved the oxidative coupling of primarily aromatic amines and phenols inside the fibers with the aid of harsh agents such as HO and NHOH. Further, the traditional process has exposed millions of consumers and their hairstylists to toxic substances such as skin sensitizers. While alternative hair dyeing processes have been explored, they fail to be competitive with the traditional method, for reasons including impracticality and limited colors achievable.