I can almost guarantee you the dog has fleas. Or.....A (meaning one) flea. Your dog is like my cat; extremely allergic to flea bites. Even the bite of 1 single flea can cause a super sensitive allergic reaction and the dog or cat who is allergic, will scratch and scratch and bite itself until raw! A good flea bath, a visit to the vet to get Frontline (a few drops between the shoulder blades works wonders) and even a prescription for steroids is what is usually required. Unhappily, allergies in humans and in pets, is lifelong. Bgail