Ethiopia, Jan. 23 -- Scientists say they may have discovered why stress makes hair turn white, and a potential way of stopping it happening without reaching for the dye.

In tests in mice, stem cells that control skin and hair colour were damaged by stress from intense pain.

In a chance finding, dark-furred mice turned completely white within weeks.

The US and Brazilian researchers said this avenue was worth exploring further to develop a drug that prevents hair colour loss from ageing.

Men and women can go grey any time from their mid-30s, with the timing of parental hair colour change giving most of the clues on when.

Although it's mostly down to the natural ageing process and genes, stress can also play a role.

But scientists were...