dog food allergies

My dog may have food allergies, what kind of food should I get for it?
I took my puppy to the vet for 8 months has been scratching a lot lately. He said it's likely she has allergies he is not sure what you are allergic. He told me to give him Benadryl for all day and bathe with a special shampoo. After doing some Internet research I have concluded that it may be food allergies. Before start cooking her all these different types of diets that I wondered if anyone had been there and that any suggestion. I realize that dogs are different allergic to different things, but any advice on a good food for dogs with food allergies would be great.
My dog has a laundry list of food allergies. I feed her Natural Balance Venison & Brown Rice formula. After 3 days his skin started to improve and the itching stopped. After 4 weeks they started introducing new foods to her one at a time for 3 days, only one per week. If you have a reaction to an allergen was positive. My dog is allergic to chicken, lamb, liver, eggs, and wheat. 3 Natural Balance dog food I could eat. She also suffers from Summer Itch. It is contact dermatitis common for dogs. They react to something in the grass when it is active in late spring / summer. I bathe my dog once a month with NUSAL-T, a shampoo of coal tar. For information about the visit of food http://www.naturalbalanceinc.com To order NUSAL-T To visit http://www.valleyvet.com tries to find a single ingredient for any meat or fish-based diet allergy visit http://www.petextras.com spent about $ 1000 at the vet before I did on my own. Food allergies usually do not manifest until the dog is about 18 months. My dog was 10 weeks. Good luck!
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