People’s grey hairs sometimes naturally regain their original colour, typically when individuals feel less stressed. The finding hints that it may be possible to develop drugs to reverse grey hair.

Lab mice go grey when stressed and the same thing anecdotally occurs in people. It has long been assumed that once hairs turn grey, they stay grey for good. But Martin Picard at Columbia University in New York and his colleagues discovered by chance that hair greying sometimes naturally reverses.