Do you see anything on the skin? Could it be ringworm?

Best thing is to take your kitty to the vet to have it checked out. Ringworm will make the hair fall out, often in a circle. It is very contagious to both pets and humans so you should definitely find out if that is what you are dealing with quickly.

My cat Jazz had it when we got her as a kitten last year and I had to quarantine her and treat her with medicine for over three weeks until the ringworm was gone.

Good luck and keep us updated.