Aw, poor Charlie. Allergies are complex and extremely frustrating. Most allergies in dogs are enviro - only 10-15% of allergies are due to food.
For year round allergies options are: Antihistamines, Temaril P (not best option), Steroids (ditto), Atopica, Apoquel, allergy testing and treatment
For seasonal allergies: antihistamines, Temaril P, steroids
Here is thread that goes into good detail about allergies:
http://www.yorkietalk.com/forums/die...tart-here.html