My cat has allergies. How do food trials work? What do they confirm?

Hi there. This is a good question! When we do a food trial, we're normally using one of two types of diets - either a hydrolyzed protein diet, or a novel protein diet.

A hydrolyzed protein diet is specially processed so that the protein molecules in the food are too small to trigger an allergic response. A novel protein diet, on the other hand, contains unusual ingredients that your cat has never eaten before - often the main ingredient is something like kangaroo, rabbit, etc. that isn't in most over-the-counter diets. Having a food allergy requires previous exposure to the ingredient that's causing it, so it's impossible to be allergic to something you've never eaten before.

So with either one of these types of diets, it's essentially impossible for your cat to be allergic to them. So when we do a food trial, we're looking to see if there is improvement in the allergy symptoms after switching to the prescription diet. If so, then that's pretty good evidence that your cat has a food allergy! If not, then she probably doesn't.

The diet trial doesn't tell us *what* she's allergic to - only whether she has a food allergy, or not. If she responds well to the diet, you can either choose to just keep her on it indefinitely (many clients choose this option, since it's easier!), or cautiously start re-introducing specific foods one at a time and watch for a recurrence of her symptoms. This is how you would go about determining what specific foods she's allergic to, if this is something you want to pursue. But you can also just feed the prescription diet long-term if she does well on it.