An anxious or playful pup may leap high quickly and suddenly “poke” at your face with their nose. That can be triggered by leaning over the top of them especially when they’re in a high-arousal situation like a homecoming or around other dogs. It may be a way for stressed pups to relieve their anxiety, so be aware of situations that cause these behaviors. Dogs control each others' movement with their body language. Think how a Border Collie makes sheep move just by getting close. You can stop your pup’s jumps by stepping close to him just before he leaps. Cross your arms and step into the pup’s personal space before he crouches to leap.
Puppies in human households try to lick the weird, flat, usually bald body part we have instead of a muzzle. When a cute little puppy jumps up to lick face, many people can only say “Awwww!” Hey presto! Jumping up has been rewarded. The puppy’s natural inclination is now a learned behavior. Too bad for the dog when he’s nine months old, bigger and less cute, muddying the pinstripes and knocking Granny to the ground.