I've been there w/ allergies as 2 of mine get irritated with all the pollens here. First, I'll tell you that food allergies account for only 10-15% of allergies, so it's unlikely that her allergies are from food...not impossible, but not likely.
Her brown patches may be pyoderma (staph intermedius), so you might want to get a skin scraping from the vet - if it's pyo, she'll need a prescription (usually Simplicef x 30 days) to get rid of it. My Wylie will get pyo a few times a year when he's exacerbated by certain pollens.
The way to approach allergies is to first recognize whether they're all year round or seasonal. If seasonal, then you may want to consider giving Temaril P or steroids during the season. If year round, then you consider Atopica and/or allergy testing and shots. My Marcel is on Atopica and it was a MIRACLE for him; he used to wake up at 1am to chew/lick his paws and Atopica stopped that. We also allergy tested him and give him custom desensitization drops so that maybe someday he can go off the Atopica.
You also might want to try, in the meantime, OTC meds like Benadryl (rarely works), Zyrtec, or Claritin...all of which are used on Dogs. I like Zyrtec or Claritin bc they work for 24 hours, whereas Benadryl or Chlortrimetron you have to give every 4 hours.
Btw, oats can irritate many allergy dogs...maybe switch carbs to something else is worth a try?
Allergies are SO frustrating and complex, so I really feel for you. But hang in there, bc you'll find something that works. We finally went to a Vet Dermatologist and they are just AMAZING. Wish I'd gone to them right away rather than wasting so much time and money with my regular vet, sigh. Hindsight, ya know
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Here is a thread from our Library that covers allergies in more depth:
http://www.yorkietalk.com/forums/die...tart-here.html