I just got a 4 year old cat about 2 weeks ago. The home he used to be in had been feeding him Iams Multicat dry food. After doing a lot of reading on this site, I decided I would switch him to a healthier dry food so I began to feed him Nutro Indoor dry food. I only had a little of the Iams (from the previous owner) that I mixed in with the Nutro, but really he mainly ate the new food as he seemed to really like the taste. He had an upset stomach just a little in the beginning (threw up once and a bit of diarrhea), but seemed to settle down from what I could see. Then, after almost a week, I noticed he was scratching behind his ears and under his neck frequently. I also noticed quite a bit of dandruff when I brushed him that I didn't think was there before. I read on here that could mean allergies so I researched a bit more and decided to give him Natural Balance food (dry) as it didn't have any corn or soy which I read could cause allergies. Now here I am a week later and he has been having frequent diarrhea and a few episodes of throwing up. I don't know what to do - not sure if it's allergies or just still getting used to the food. Does anybody have any ideas? He is fine otherwise and eats a lot, just doesn't appear that these foods agree with his stomach. I don't want to have to keep switching around foods so I could really use some advice.