My cat Puffy has been suffering from some mysterious skin infection for the past four months. A biopsy was sent to the UofPenn and came back negative. No sign of viral or bacterial infections. The vet-dermatologist diagnosed him with some type of food allergy and he is on a low allergin food now. In the meantime, he has this extensive rash on his head and neck, a patch on his back, and areas on his inner legs and belly. I've been treating the rash with aloe vera with good results, but he is still itching and throws up large fur balls every week or so. HELP!