If it's scabby, then there is definitely something going on here like allergies. Scabs usually mean there is an infection, called pyoderma in dogs -- and it needs to be treated w/ Simplicef for 30 days. The longer you let it go untreated, usually the worse and more profuse it will get.
For allergies read here:
http://www.yorkietalk.com/forums/die...tart-here.html