There is a medical obsessive/compulsive type disorder called trichotillomania. I've only ever looked after 1 child with it - and she was pretty severe.

I'm not a psychologist (just a child health nurse) - but I would see how it progresses. Do you give your child more attention when you notice the hair pulling? That could be a reason why they started??

I would see how it goes, but if you are concerned, or it starts to get worse, I would consult your local child health nurse or your GP.

Good luck!!