Chocolate Lab Allergies/food recommendation

Question
My 1 1/2 year old chocolate lab is experiencing hair loss around her ears, eyes, and down her nose.  She has one spot on her side she is now missing hair from, from the constant itching.  She also has ear infections/swelling.  I have been to the vet twice for these issues and they prescribe a steroid, ear solution, and try to push Science Diet ZD.  I'm very close to trying it because I feel so bad for my dog.  I'm wondering if there are other alternatives to Science Diet ZD before I jump into the price trap?  Mylah was originally on Purina Puppy Chow, then Beneful Original, and I tried Diamond Natural Lamb Meat and Rice.  Any suggestions?

Answer
You can use any single protein source food as long as you do it for at least 6 weeks.  That means no treats, flavored heartworm pills, or any table food.  Using z/d takes the guesswork out of diagnosing food allergies.  The protein in z/d is broken down into very tiny molecules so that the dog's immune system does not recognize it as a protein.  If the dog responds in 6 weeks to the z/d food trial, then you can start adding other foods to see if she reacts to it.  If there is no response in 6 weeks, she probably is not a food allergic dog.