I'm sure many of you have experienced this - you scratch your back or brush your hand over your arm and find a ridiculously long thin white hair, sometimes as long as 3 or 4 inches. I know a few people who get these quite frequently, and anecdotal evidence seems to suggest they almost grow almost overnight. A quick Google search for "single long white hair" throws up plenty of references to them, and various beauty advice, but I'd like to know the biology behind them.
- What triggers abnormal body hair growth?
- What causes these hairs to grow so much longer than other "normal" body hairs in physical proximity?
- Why are they so thin and white compared to other body hair?
My primary hypothesis is that the hair cell grows rapidly in an uncontrolled manner, similar to how cancer might, and that the unusual appearance is due to the cells being starved of nutrients. I may be completely wrong, though.
I'm mainly interested in humans here, but if more in-depth research is available on animals that'd be interesting too.
