The Scratcher

Hi! My sister has a 13 year old spayed female cat named Inara. Inara is strictly an indoor cat, and the only pet in the house. A few months ago, Inara began scratching her neck a lot more than usual, and my sister had found a bunch of scabs where she was scratching. The scabs were about the size of individual rice krispies- reddish brown and raised. The scabs were only in the neck area, and there doesn't seem to be any fur loss. Inara eventually broke the skin with her scratching, so we put claw covers on her back claws. That stopped the bleeding and scabbing, but as soon as the covers started falling off, she started scratching again. We don't think it's fleas- we've seen those on cats before- this looks different, and we have checked and not found any flea dirt. She has been to two vets but they have not offered any solutions besides the claw covers. Inara seems to be healthy otherwise, still eating, sleeping, peeing, pooping, playing, and being affectionate. Her last vet checkup was 4 months ago and she got a clean bill of health. Any ideas what this might be? 

Has your sister changed Inara's food, or have any changes been made by the producer of her usual brand(s)? One possible cause of itching is a food intolerance.

Thanks for responding! No, she has not changed food since my sister adopted her 3 years ago, and as far as we can tell there have not been any changes from the manufacturer. Is it possible to develop an intolerance over time?