Experts predict that permanent hair dyeing will become longer lasting with more natural-looking dyes and gene therapy to reverse the gray. Most permanent hair colouring technology uses a 150-year-old approach that uses p-phenylenediamine (PPD), a chemical that produces darker, browner shades when exposed to air.
However, there have been safety concerns over 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.
Future hair colouring techniques include nano-sized colorants composed of pigments 1/5,000th the width of a human hair, which will penetrate the hair and remain trapped inside for longer-lasting hair coloration.
Scientists also are developing substances that stimulate the genes to produce the melanin pigment that colours hair.
Other new technologies may stop graying of the hair or prevent its formation altogether, the scientists say.
The article appears in ACS's journal Chemical Reviews.