Depends. Daisy likes to lick at our mouths after we eat something she thinks smells delicious, but more often than that she licks our faces when we get home in the evening, before we go to bed, and when she thinks she’s in trouble. I say it’s just affection.
I don’t understand those people that won’t let their dogs give them kisses. I’d never let just anyone’s dog lick my face unless they’re puppies or just too damn cute to resist, but my dog can lick me as much as she pleases. It makes me feel all warm inside. :)