An interesting one, this.
The question of self mutilation in dogs is one of the most frequently asked 'why does my dog' type questions according to Google's search stats. According to Wapedia dogs, like people can suffer with obsessive-compulsive disorder (OCD): PetLibrary advises: A complete veterinary evaluation should precede the behaviour program for rehabilitation. Flea or tick infestation must be ruled out as a cause. Possible allergies also should be considered, as the problem in many self-mutilators stems from food or other environmental allergies. Many practitioners recommend hypo-allergenic diets, even in the absence of clinical symptoms, as a matter of "insurance."