Are the 2 dogs related...? If yes, then I'd think some like allergies in both. If not related, then I'd think something contagious like ringworm (which can itch in dogs and cause hair loss), mites, flea bites, or something chemical perhaps.
Do they lick or chew at their paws...? If yes, think allergies. Read more about allergies here:
http://www.yorkietalk.com/forums/die...tart-here.html