Dogs that bite can be very dangerous to other dogs and humans. Almost every puppy will instinctively bite, but there are ways to teach a dog that biting humans is not allowed. Some dogs will bite out of fear or aggression, and these dogs are very difficult to train. Punishing a dog for biting should be done with caution; if not done correctly it can make your dog more aggressive and make the problem worse.
Put your dog in a timeout when it bites. According to the United States Humane Society, giving a dog more attention when they bite is reinforcing its biting habit. The best thing to do is to completely ignore your dog by putting it in an isolated place without toys or people for a short time. The dog does not need to be alone for very long, and it should still be provided with fresh water at all times.
Squeeze the dog's muzzle to put its lips into its mouth. When a dog is biting down hard on you, put your hands around its mouth and gently fold its lips into its mouth. This will cause the dog to bite down on its own lips and cheeks, and will teach the dog that biting other people will cause pain to itself..
Use a taste deterrent on your hands. There are products such as Bitter Apple and Bitter End that taste bad when the dog bites down on them. Cover your hands with the product so that the dog will taste the bitter flavour when it bites. This is a safe and humane way to punish a dog for biting and deter it from biting you again. Taste deterrents are available at most pet stores and veterinary clinics.
Consult a professional pet trainer if your dog's biting is threatening other people or dogs. Socialise your dog properly and use positive reinforcement training methods at all times to prevent biting.
Hitting your dog back when it bites you can actually cause your dog to bite harder in response. Do not pull your hand back when your dog is play-biting, as it can make the dog think you are playing a game.