This doesn't sound right to me...food allergies are actually *very* rare - they only account for about 10% of dog allergies. Also, the only real way to discern a food allergy is to do an elimination diet, was that done...? It's more likely (especially bc it started in summer too) that they're seasonal allergies. Benadryl is not great for allergies bc you have to give it every 4-6 hrs for it to be therapeutic. Vet Derms recommend Claritin or Zyrtec as they're 24hr meds; and then there are the more effective prescription meds.
You should def read this whole thread:
http://www.yorkietalk.com/forums/die...tart-here.html