analysis of almost 500 articles and patents on the chemistry of permanent hair dyeing, which foresees much more innovation in the years ahead, including longer lasting, more-natural-looking dyes and gene therapy to reverse the grey.
The article appears in ACS's journal Chemical Reviews, where Robert Christie and Olivier Morel note that hair dyes are poised for expansion in the future due to the greying of a global population.
Most permanent hair colouring technology, apparently, is based on a 150-year-old approach that uses p-phenylenediamine (PPD), a chemical that produces darker, browner shades when exposed to air. Concern over the safety of PPD and other hair dye ingredients, and demand for more convenient hair dyeing methods, has fostered an upswing in research on new dyes and alternative hair colouring technologies.
The scientists describe progress toward those goals. Future hair colouring techniques include nano-sized colorants, for instance. Composed of pigments 1/5,000th the width of a human hair, they will penetrate the hair and remain trapped inside for longer-lasting hair colouration.
Scientists also are developing substances that stimulate the genes to produce the melanin pigment that colours hair. These substances promise to produce a wider range of more natural-looking colours, from blond to dark brown and black, with less likelihood of raising concerns about toxicity and better prospects for more natural results.