Hair falling out in patches?!?

Just a quick question here: my 11-year-old just lost a small patch of hair—specifically, a little tuft that had actually turned gray on its own before falling out. It’s just that one specific spot. Is there any reason to be worried about this, or could it just be some kind of localized allergy? What should our next move be? Thanks in advance!

Was there any kind of impact or blunt force trauma to that area? Either way, you really ought to go see a doctor. This isn't normal...