Yes, it is common very common.
Some children go completely bald to come back with new hair, sometimes a completely different color. Never happened to my children, but their hair did get thinner. I myself born with cold black indian hair, fell out all the way around 6 months, then came back almost white. I had blond hair until 8 then turned dark brown again.
Mom said I was so bald, and hair so lite I looked like a boy!!! Lol