We have a stray long hair with a similar cat skin problem. The cat may be 2 years old and loves to scrape. He is neutered.
He got a scratch or bite one day when he was out. We washed the area with peroxide and vitamin E liquid. He started to heal very well but now he scratched the other ear and the top of his head is covered with crusty scale.
We no longer let him out, we bathe the area twice a day to remove the crust of the scales. They remove easily.