My dog had the same problem, the vet said it was fleas, although we never saw many on her, but the vet insisted that she had developed an allergy to fleas and gave her a steroid shot, then another, then another, but we couldn't keep spending all that money, especially since they became less and less effective. At the time our son was living in the house with his young daughter and when Tara's personality started to change, we had no choice, but to put her down. One of the hardest things I have ever had to do, but we had over 8 wonderful years with her, and Shepherds don't usually live much more than that. Hope you find the right answer.