Love it or loather it, face-licking is a common and natural canine behaviour. Rather than simply being the equivalent of an affectionate doggy kiss, it signifies different things depending on the situation. It might express pacifying or submissive behaviour, respect, that they???re just pleased to see you, wants something, is hungry ??? or perhaps simply enjoys the salty taste of your face.
To understand why they communicate in this way, it???s worth remembering that dogs are introduced to licking as soon as they???re born, when their mother licks them to clean them. Later, pups lick and clean themselves and their pack members, strengthening social bonds.
In the wild, wolf pups lick their mother???s face and mouth when she returns from hunting, causing her to regurgitate some food for them to eat ??? so your dog may be asking for a snack when he does this to you.
Adult dogs use face-licking to show respect to more dominant dogs, so a slurp from your pooch may similarly express his deference to you ??? or the sentiment: ???I???m like a puppy, I???m dependent on you, and I need your help.???
If the face licking gets obsessive, though, seek advice from your vet on how to curb it.
Source: Deirdre Vine