Cat’s Neck - Fur Missing In Front

Question

I just noticed a large bald spot at the front of my 10 month indoor Calico. It was not there yesterday. I removed her collar with a bell and charm as well as the Seresto collar. She has had both on for a couple months. She rubs her neck on furniture legs and door frames. The area is not wet or sticky; it is smooth and soft. I put Neosporin on it and touching it does not appear to bother her. I am not putting collars back on her. Has anyone else had this occur? Thanks for any help.