I somehow missed this thread so I'm not sure what's happening w/Charlie's foot. But I can relate to you what was going on w/my dog Charmin years ago. She constantly licked her paw, vet didn't know why, to the point where she would form a huge blister on the top of it. I would soak it in warm Epsom salts and that would cause it to pop, all the stuff would come out and the Epsom salts helped it to heal. I realize dogs have different temperaments from cats but you might give it a try. It certainly couldn't hurt Charlie and he might enjoy it because it's soothing. My vet bandaged her leg clear past the second joint to try to keep her from licking and chewing on her paw. But I'd come home from work and find the entire bandage, looked like a leg, lying on the floor. She'd somehow manage to get the entire bandage off w/out having to unravel it. She was determined! My vet thought it was an obsessive thing w/her and she continued it til the day she died! Maybe this isn't the case w/Charlie. I'm just throwing around an idea here for you to consider. At any rate, why not give the Epsom salts a whirl?