How old is your puppy? Mine did the same up until he was about 3-4 months old. He is now 5 months old and anybody can pet him without having their hands chewed up. The change happened rather suddenly, but he is now teething, so the mouthing has not fully disappeared yet. Keep in mind that this is normal, up until about 6 months of age, when his adult teeth have fully emerged. However, I tried to inhibate his biting of human hands (lol) by saying a firm 'No!' and then offering him one of his toys in his mouth or rawhide bones and such - these were his favourites. Good luck and lots of patience, it's worth it!
