[KJohnson]

A couple months ago (around February) Westin got fleas pretty bad, and we didn't know becuase he had just gotten neutered, so he had the cone collar on. By the time we noticed, he had them all over, so we got him on Advantage and they all died off about a week or two later...
Recently, Westin has begun scratching again and I saw a couple fleas, so I re-administered the Advantage a couple weeks earlier than his 6-week-apart treatments (this was on Wednesday night) yesterday, my boyfriend noticed that Westin is still scratching and biting himself. So much so, in fact, that he has started to bite his skin raw and start bleeding. I can't see any more fleas and I haven't been able to find any reason for his biting and scratching- no noticeably dry skin or anything. I was wondering if anyone had any previous experience with habitual biting or had any idea what could be going on.
I have heard that if scratching becomes a habit, dogs will do it just because they feel the need to, even until bleeding. Has anyone heard of this?