Hi Misti-
If you are truly concerned that your dog might have a food allergy, the first place to start is with an elimination trial. This will be the best way to spend your money.
You will need to discuss this with your vet, but what you would do is get a prescription from her/him for a hydrolyzed protein theraputic diet. She can eat that food and only that food for usually about 3 months. No treats, no flavored meds, no table scraps, nothing.
These foods are extremely different from over the counter limited ingredient foods on several levels. One, the companies sterilize the machines that are processing the food before they run the hydrolyzed protein diet each and every time. This makes certain that the food is not being contaminated with other proteins. Secondly the hydrolyzation of the proteins makes it so that the immune system can not react to the food at all. This is not the same for OTC limited ingredient foods.
This is going to be the best route to take instead of purchasing LID foods from a pet store.
