After decades of over-vaccinating dogs, allergies in dogs are staggering! They're super common now, sadly.
Benadryl almost never does a thing. Claritin and Zyrtec rarely work, but sometimes can.
If/when allergies are bad, you then truly need to consider prescription level options like Temaril-P, Atopica, Apoquel, steroid.
Read this whole thread - tells you more about this:
http://www.yorkietalk.com/forums/die...tart-here.html