From the get go, you should realize that this is not a dogs fault. Instinctively to learn about the world, to play and to be social puppies mouth each other. There is rarely any malice and its an acceptable method of learning how far they can go, because a dog bitten too hard will really let the biting dog know.
The issue happens when a puppy doesn’t learn what a reasonable amount of pressure is or doesn’t grow out of it all together. Puppies might start mouthing for fun and playing, but usually continue for quite a while as they adjust and sooth their second set of teeth pushing through.
That is the reason we give dogs long lasting chew treats or chew toys, to distract and redirect their chewing energy to harmless objects – not to reinforce behaviour.
The thing is moist dogs grow out of puppy mouthing as they move into adulthood. By the age or 1-2 dogs can still puppy mouth other dogs when playing but the owners SHOULD have taught their dogs that it is NOT appropriate to chew on a human like that. Because some owners get a kick out of this primal action, they might allow the action on their hand or pants for longer than is desirable to assist a dog kicking the habit.
Why your dog puppy mouths
1 Another hand – Dogs don’t have opposable thumbs so they use their mouths much more than humans do to interact with the world. They use it like another hand.
2 Primal instinct. Just like dogs love to chew and chomp on a bone, they love using their mouths to touch and rip things apart. They are in training to do it for real on a prey hunt and all the nuances of puppy mouthing help them develop the coordination and strength they need later in life.
3 Dog play – Dogs play much more than many other species, well into old age. Their ancestor the wolves are huge plan fans, but only as puppies, it gets all a little too serious in sorting out pack order to play and lose as an adult. Play is for fun, to release endorphins – because a world without fun, even for a dog isn’t worth living.
4 Teething – A legitimate reason to mouth, but you have to redirect that energy to strong rubber toys and the like, not furniture and human body parts. if not directed to good things to chew, this will become a habit that no one will like later in life.