I have a middle aged cat named Sally. She recently has begun to show signs of itching and scratching along her back and neck. Doesn't seem to be really bad but it happens often enough. I read this is likely a food allergy. She used to gobble down the cheaper purina cat food without complaint but would ask for wet food too. She has shown decreasing interest in her usual dry food, and her vomiting increased. I had bought her the expensive brand that is grain free but she would pretty much refuse to eat that. I just bought her purina Sensitive Skin & Stomach Formula and that seemed to help for a bit. She threwup less. However a week and a half later she is being stubborn with eating her food and still itching. I bought her higher quality wet food too but she is iffy with that as well. She is acting otherwise healthy and strong but this is a point of concern. Any tips from other owners with this problem? Would a more expensive brand of sensitive stomach food work?