Everyone says you should never put your face anywhere near a dog's mouth. That's probably sage advice for most people. But as a dog lover, I know that dogs are honest. A dog normally isn't going to pretend to like you and then bite you. 99.9% of the time, humans have all the warning they need.
Ty doesn't have a mean bone in his body. He would sooner bite his own face than bite mine. He would be more likely to take a bite protecting me than to bite the hand that feeds. He is a typical, well-adjusted male dog. Now, Ty has bitten human strangers before, but only people who mistreated him, and unsupervised children who didn't know any better. Some people shouldn't own dogs, and they shouldn't have even briefly owned Ty. At any rate, he's back with me now, and his loyalty is totally unconditional to anyone who earns his trust. He's the perfect dog.
Zoey is like a daughter to me. Our life is about snuggles and kisses, some of which happen when I'm asleep. I almost have been nipped a couple times in my sleep because when Zoey and I are cuddling, if Ty wants to come join us, he has to go past Zoey under the blankets, and when I am asleep, she will nip at him. He obviously doesn't want to be nipped by honey bunny, so he will move out of the way with his young dog reflexes, causing her to miss. Zoey does have a few mean bones in her body, but just like Ty, she would never intentionally hurt me.
Spot has bitten me, but I still let her give me kisses. When she's being sweet, she's just as lovey as her daughter. But she's been a mommy, and sometimes she doesn't want anything to do with people or dogs, which she is very clear about. And that's the thing: anyone paying attention can easily read what a dog is telling them. Clipping her nails is the hardest, because she will go from barely tolerant to trying to bite my hands with no warning. Which is why I paid the vet to do that last time, and they were very careful. But again, she can be as sweet as Zoey, and it's always clear what her thoughts are.
Smokey is my grumpy old man. He is more like Ty but for different reasons. If I wasn't bigger, stronger and with all the food, he wouldn't respect me. If he bit me, then he would get less food. I'm the boss: the "pack leader" the dog whisperer talks about. Smokey loves jumping on people's laps and giving them kisses before they can react to stop him. They say "ooooh cute, he's giving me a kiss" and I say "well, it's more like he's a) smelling your breath to see what you've eaten and b) sucking up to you for more food." But it's the same effect as Ty: Smokey would never purposely hurt a non-aggressive human.
I will let a new dog sniff my face as a sign of friendship if it is being friendly. It's all about the dog's body language, and like I said, dogs are honest. It's cats that lie.