See The Consequences Of Allowing Your Dog Lick Your Face

Letting your dog lick your face can potentially kill you.
Author and dog expert Marty Becker told Doggies Care :
“They raid the garbage can. You know, we give each other a peck on the cheek when we say hello, they give each other a peck on the rear end.”
John Oxford, professor of virology and bacteriology at the Queen Mary University in London, painted a graphic picture of the bacteria present in your dog’s mouth and muzzle.
“It is not just what is carried in saliva. Dogs spend half their life with their noses in nasty corners or hovering over dog droppings so their muzzles are full of bacteria, viruses and germs of all sorts.”