I saw my mother-in-law's cat for the first time in several months yesterday, he has always had mild skin problems, he'll chew on his legs and make a raw spot, but he has gotten really sick. He has chewed a hole in his side about 6'' in diameter, with open sores from biting himself. He seems like he's constantly itching, constantly in pain. This broke my heart, she doesn't have the money to care for him the way he needs to be, I'm sure there is probably no real "home remedy" for his problem, but do you have any idea what could be causing this? Maybe allergies?

Optional Information:
Age: 5; Male; Breed: Orange Tabby

Already Tried:
Benadryl, aloe cream