What makes our hair turn grey?

Chris - The reason that hair goes grey is naturally it's a white colour. That's the colour of the protein, keratin, that hair is made from. You have in the hair follicle which is a special ring of stem cells in the surface of your head, under your arms and other areas of your body cells called melanocytes. These make melanin, the same stuff that gives you a sun tan when you go out in the sun. Melanocytes add to the hair melanin. They add different chemical forms of melanin: pheomelanin and eumelanin. This is a dark colour. Depending on what ratios you put in and how much is in the hair the hair goes darker. If you have, for some reason, a loss of those melanocytes they stop making melanin and the hair goes back to its natural white colour. What happens is as we age the melanocytes burn out. They stop making this particular chemical and as a result you go grey. As to whether it goes grey overnight I think you looked into this, Kat, the answer was it's more likely that people's hair might fall out and then it comes back white because they were going to go grey anyway.

Kat - Exactly it's very unlikely to go white over such a short length of time.