There are various reasons for destructive chewing. Pups need to chew when they are teething between the age of four to six months. They are like babies putting everything in their mouths. This is a pleasurable and necessary experience for them and must be handled properly or a chewing habit may be carried into adulthood. The best way to handle this problem is to soak several old wash rags in water, squeeze them out, and put them in the freezer. Whenever you catch your pup chewing, give him one of these frozen wash rags. The coldness will soothe his swollen gums.
Older dogs usually chew to release tension. There are several things you can do to help your dog feel more at ease. Try to avoid emotionally charged departures. When you leave, just say, "Good-bye, see you later." The greater fuss you make, the more anxiety you create. Establish your leadership through training. Dogs are more secure knowing they have a leader. Do not give in to his demand for excessive attention when you are home. The more you give, the more he will want and, when you are not there, he will be frustrated. Do not isolate your dog as punishment for chewing. This will create more tension and lead to more chewing. Do not physically punish him for chewing. He is chewing to relieve tension, and punishment creates more tension, hence, more chewing. Instead, give him plenty of exercise before leaving him home alone. Exercise works the same way for dogs as it does for humans. It relieves tension.
If your dog insists on chewing, there are some things you can do to slow down the habit and redirect the chewing to permissible objects. Do not play tug-of-war games. This stimulates the oral/mouthing response. Get him a toy-box and fill it with permissible chew toys-nylon bones, racquet balls, rubber rings, and nylon rope. Do not put any personal belongings in this box such as old slippers, knotted socks, or any leather or fabric items. Whenever he chews on a personal belonging, say, "NO CHEW!" and lead him over to his toy-box, give him one of his chew toys and say, "CHEW," followed by "Good Dog!" This will teach him that he can chew but only if the item comes out of his toy box. If he has a personal item in his mouth, do not pull it out. Instead, distract him with one of his toys or a food tidbit. If this does not work, blow a whistle, pop a balloon, or blow a horn. A loud noise will cause him to release. Physical punishment for having this forbidden item in his mouth will only serve to reinforce this behavior. In other words, the chewing will continue and will, in all probability, increase in frequency.
The key factor in anything that you do is to establish a bond with your dog. It is essential that you spend time training him. Part of any good training program includes breaks for playtime. And, of course, lots and lots of daily exercise is absolutely necessary for reducing the stress of being left alone for long periods of time.
Follow this advice and you will establish a bond with your dog wherein he will see you as his leader and he will always try to please you.