Canine acral lick dermatitis (ALD), or lick granuloma, is a serious self-injury to a dog’s skin caused by obsessive licking. The most common spot for ALD is the front side of a forelimb, somewhere between the toes and the elbow. Acral lick dermatitis is most commonly seen in large breed dogs.
If the dog has no behavioral abnormalities other than constant licking, while the licking may escalate into an obsession over time, chances are it isn’t rooted in OCD or another psychological disorder.
Full article Healthy Pets: Why You Shouldn’t Ignore Your Dog’s Obsessive Licking