01/06/2026
Your hair doesn't turn grey, it grows grey. That one distinction changes everything about how greying actually works.
Every strand starts completely colourless. The colour you see is actively injected into each strand by specialised cells during the growth process. When greying happens, it means that system has started to fail. And the mechanisms behind it are more specific than most people realise.
Melanocyte stem cells get physically stuck in the wrong part of the follicle and stop receiving the signal to produce pigment. Hydrogen peroxide, which your follicles produce naturally, builds up as we age and bleaches the hair from the inside. And stress has a documented biological mechanism, a 2020 Harvard study found it directly depletes the stem cell reserve.
The encouraging part: those stem cells aren't dead. They're stuck. Which means research is now asking whether greying might one day be partially reversible.
Our team explored the full science on the So That's Why podcast, link in comments 🎧
Did you go grey earlier than expected and does it follow a pattern in your family?