Is there a single cat food for food allergies and lower urinary tract disease? He has a history of struvite stones and the doctor suspects a food...

Royal Canin makes novel protein foods that would be fine for the urinary tract.  When it comes to the urinary tract always make sure that your cat is getting enough fluid.  Giving canned food which is 75% water can help.  Remember cats refuse to drink water out of a bowl when it drops so far below the lip about an inch or two.  If your cat goes into the shower or bath tub, is facinated with dripping fauscets and seems to bat the water out of his bowl, he knocking it out of the bowl to drink it.  Always have at least 3 water bowls and have a container with water and you can easily keep topping the bowls and he will then drink more water,and won't do the other things as much to get water.  As far as the vomiting goes, if your schedule permits, the more frequent you can feed your cat smaller amounts will help.  Five to six small meals per day is very good for the cat's GI tract.    Examples of novel proteins are venison rabbit  turkey and duck.  Your looking for something that the cat has not been exposed to before and this may also help the vomiting. Science diet makes a diet for hair balls, which can really help that problem