Grey hairs sometimes naturally regain their old colour, typically when people experience reductions in stress. The finding hints that it may be possible to develop drugs to reverse greying
Source:
https://www.newscientist.com/article/2244772-grey-hairs-sometimes-regain-their-colour-when-we-feel-less-stressed/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home