My 7 year old male constantly licks.. He licks his sister to the point she has to walk away or else she finally snaps at him. He licks people any possible time he can. He licks his paw excessively. He even licks the air constantly. This has been going on for months and it never gets better. I have corrected him over and over, nothing helps. Any ideas why he does this and also how to stop it???