The shirt destroyer

Not sure what is going on with my dear, sweet Cai, but I'm about to lose my mind. He keeps sucking and chewing on his shirts to the point where washing them will not refresh their collars and little holes are appearing! Is there something psychological that I should be worried about? A nutritional deficiency maybe? Not sure if I should ingore it, punish it, or something else. After he walked in with red shirt fibers on his face, I told him if I see him doing it again, he is going to have to go shirtless, which would embarrass him. We'll see what happens...