Scientists discover why hair turns grey—and how to reverse it

A new study has uncovered why hair turns grey as people age. Researchers found that stem cells responsible for hair color get trapped in hair follicles, stopping them from regenerating into pigment cells. The discovery, published in Nature, suggests that restoring these cells' movement could reverse grey hair.

The research team, led by Ya-Chieh Hsu from Harvard University, focused on melanocyte stem cells (McSCs). These cells normally travel between two compartments in hair follicles: the bulge and the germ. When they move freely, they mature into pigment-producing cells, giving hair its color.

As hair follicles age, more McSCs become stuck in the bulge compartment. Unable to return to the germ area, they fail to regenerate into pigment cells. This blockage coincides with the rise of grey hair in both humans and mice. The study also noted that McSCs decline earlier than other adult stem cells, explaining why grey hair often appears before other signs of ageing.

While stress speeds up hair follicle ageing, the researchers clarified that it does not directly cause grey hair. Instead, the loss of McSCs' mobility is the primary factor. The team now plans to investigate ways to free these stuck cells, potentially restoring pigment production and preventing grey hair.

The findings provide a clear link between grey hair and trapped stem cells. If scientists can reactivate the movement of McSCs, it may be possible to maintain natural hair color for longer. The study opens new avenues for research into reversing or delaying hair greying.