The declawing happened over five years ago, when he was still a few months old, so I doubt that's the cause. And as for the illness, I did think of that...but then why is he so happy as soon as visitors leave? If he was sick, he'd continue to be upset, wouldn't he?

At first I tried ignoring him when he would get upset, but nothing changed. We stopped spritzing him with water when it stopped working. He even found the spray bottle at one point and chewed it all full of holes so the water would drain out.

I can try shutting him away in another room, it will just mean I have to get him into a room and the door closed before I even let the visitor in.