Many dogs are put to sleep by owners who can no longer figure out what to do with a dog that barks or howls constantly when they are gone, destroys things in their absence and basically makes a nuisance of himself. These people do not understand that the dog is not being disobedient—he is most likely suffering from separation anxiety.
Dogs are pack animals. As his family, you are his pack. When you leave him alone, he feels lost and scared. Often loud noises will frighten him. His howling and destructiveness are the only way he has of showing his displeasure. You can help him get through this with patience.
Try to find a room where he feels comfortable—one that isn’t close to a street or other traffic. If possible, buying a crate made specifically for the size of your dog will help him feel more comfortable. Placing a loved toy and an item of clothing that smells like you inside with him will increase that comfort.
Start by leaving him only a few minutes at a time. He needs to be confident that you will return. You can gradually extend the amount of time as he becomes more comfortable. Praise him greatly for every time he waits quietly. If all else fails, talk with your vet and see if he can prescribe some type of anti-anxiety medication to give your dog when you need to be away.