Licking is a very common dog behaviour and like any trait, it can vary hugely from dog to dog. Some love it while others hate it, but licking humans can occur for several different reasons.
In the wild, young wolves will lick around their mother’s face to interact, request feeding, and demonstrate submission to an older animal. As they grow, they still lick around other wolves’ face’s to communicate, detect pheromones, or show submission. To some extent our domesticated dogs still express these traits. Dogs will often be seen licking around the muzzle of dogs they meet while out and about as a means of communication. Dogs in a strange situation, such as at the vets, may lick the face of a stranger to try and determine their intentions, or to appease (i.e. say “please don’t hurt me”). Our pet dogs also lick to demonstrate affection, especially with people they’re closely bonded to.
If you watch the canine-human interaction, short sharp licks to the chin or nose, with wide eyes and ears back is a sign the licks are inquisitive or submissive. Big sloppy kisses with ears forward and relaxed body language is much more suggestive of a happy dog simply delighted to see his/her human.
We taste good
It might sound disgusting but to a dog our skin can be a world of smells and flavours. Whether it’s the remnants of what we had for lunch, the smell of everyone else on the train home, or simply the natural taste of our skin some dogs can’t get enough!
Because we reward them
Regardless of the cause of the licking, most people will respond to a big sloppy kiss in a positive way. Whether you squeal and wave your hands, or embrace your dog with extra ear scratches and cuddles, we tend to react in a way that dogs enjoy. Animals are finely attuned to our responses, and over time this positive feedback will encourage licking as a form of greeting.
Most domestic dogs will lick for good reasons; affection, information gathering or habit. But what happens if your dog licks too much? A dog that performs obsessive licking can rapidly become unpleasant, and no obsessive behaviour is a healthy trait for a dog. Certainly the first step to discourage licking is removing the positive feedback. Licking often accompanies other problem behaviours such as jumping up. The simplest method to try and reduce these behaviours is to ignore the dog; turn your back until the jumping/licking has ceased. Once your dog is calm with all four feet on the floor, proceed to greet them as normal. Over time most dogs will realise that the fastest way to get what they want (attention) is to avoid the licking.
If you feel your dog has a real problem with licking, please see your vet and/or a registered veterinary behaviourist.