Dogs lick everything, and among many other common dog behaviors, licking is near the top. Dogs use their mouth and nose to explore the world, so it's not surprising that dogs lick everything. Licking is natural for dogs, like a habit. They'll lick themselves, other dogs, random objects, and one of their favorites, you!
Dogs usually lick themselves to clean or groom themselves (it's not just cats!). As long as it's not compulsive, it's completely normal. In dogs, licking releases endorphins that give them a sense of comfort and pleasure. It's comparable to when humans bite their nails; it relieves stress.
When or if it becomes compulsive licking, there may be an underlying medical condition. Dogs will lick open wounds and hotspots as a healing remedy because their saliva contains enzymes that help clean and heal wounds. However, it is common in dogs that they will lick a wound too much and make it worse. Additionally, they will lick themselves to soothe their joint pain. Dogs that lick their anal area may be suffering from allergies or need their anal glands expressed.
From when they are born, the mother communicates with her puppies by licking them. Licking is how she stimulates them to start breathing when they are born as well as to stimulate their bowels when they are still nursing. As the puppies grow up, they lick around their mother's mouth as a submissive gesture, which is a behavior that stays with them when meeting other more dominant dogs.
Like previously mentioned, dogs explore the world with their mouth and nose. So, when your dog licks random objects, like the wall, it's likely he or she is only trying to figure it out. If it's becoming a habit and your dog is licking random objects non-stop, it could stem from a behavior issue. Compulsive licking could be a sign of anxiety, fear, and obsessive-compulsive disorder.
The simplest answer is that they like the taste. Humans' sweaty and salty skin is delectable to some dogs and they want to get a taste, no matter how gross it is to us. If it's become a habit, it could be because you unintentionally rewarded the behavior, encouraging your dog to continue licking you.
Dogs will also lick their humans as a sign of submission, as they do with other dogs. Your dog may see you as the alpha in the pack and will show his or her subordination.