Monica Segal has a brochure on doing a true elimination diet, and otherwise managing allergies: http://www.monicasegal.com/catalog/product.php?cPath=25_26&products_id=72 As someone with a severely allergic dog, I've read her stuff and she is right on the money. I wish I'd gone this route eight years ago instead of messing around with commercial products.
Anyway, the first thing that most allergists (veterinary specialists) recommend is putting your dog on a diet prepared at home that consists of one novel protein source, and one novel carb source. Then you feed nothing but that for, I think it's two months. If your dog has been on a healthy diet up to now, she should have plenty of reserves available to make up for such a diet being slightly unbalanced.
After that, it's up to you how to proceed. If there was enough of an improvement that you'd want to continue with the simple diet for life, you just have to get a nutritionist to tweak it so that it's balanced - usually with a custom blend of supplements. Or, you can slowly introduce more familiar ingredients one at a time to try to identify what's bothering her. Or, you can take her to an allergist and get tests run to try to determine what she's sensitive to. Other than some really good detective work, that's the only way to tell whether she's got allergies to environmental allergens like dust mites and pollen.
I recommend, whatever you do, start a journal that summarizes your dog's daily symptoms, weather, pollen count, what you fed, anything else you did to her, activities that might affect her (like if you cleaned house or sprayed bugs), anything you can think of to jot down. Vets love this stuff and it will help you get tons more out of any vet visit on this issue.
Good luck!
Becca Shouse
Maggie and Zhi (queen bees), Ben, Gus, Cord, Rocky, Ted (BCs), Lu and Tully (Maremma flock guardians)
Irena Farm, Semora, NC
