Why do dogs lick people? © Getty

Why do dogs lick people?

Be warned: the answer involves more regurgitation than you might think.

Here’s a question for anyone forced to wipe canine saliva off their face today: why do dogs lick people?

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Unfortunately, at the moment, it’s not possible to know exactly what dogs are thinking as they try to mop your entire face with their tongue. However, experts have several ideas about the function of this behaviour.

The foremost functions: dogs lick you to say hello and gain attention. “It’s essentially a social behaviour that comes from their evolutionary history,” says Dr Emily Blackwell, lecturer in companion animal behaviour and welfare at the University of Bristol. “It’s a greeting and can be taken as a compliment.”

So far, so adorable. However, the reason dogs instinctively carry out this behaviour is less sickeningly cute and more just a bit sickening. “Puppies generally learned to lick their mother to greet her, and also encourage her to get food. The mother will then regurgitate material for the pup to eat,” says Blackwell.

Now, this absolutely does not mean you should immediately vomit on any dog that licks you. Particularly if it’s a stranger’s. As Blackwell says, for adult dogs, this is primarily a social behaviour and meant as a greeting.

Why do dogs lick people? © Getty
A dog offering a (very sloppy) greeting to a human © Getty

Interestingly, Blackwell adds that it’s rare you’ll see an adult dog licking the face of another canine – it’s simply a puppy-like behaviour dogs perform for humans. Why? It’s thought that by becoming a dog’s primary caregiver throughout life, we encourage a kind of life-long puppyhood.

“You can see other prolonged puppy behaviour in domesticated dogs,” says Blackwell. “For instance, simply the level of vocalisations that we see in domesticated adult dogs is far more like that of puppies than non-domesticated domesticated adult dogs.”

This retention of juvenile behaviour into adulthood even has a name among experts: neoteny. And it’s not only common to dogs, but other domesticated animals, such as cats (see: Why do cats knead?).

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Currently, there’s no consensus whether encouraging juvenile traits in our pets is a good thing or not. However, according to Blackwell, we should at least be aware of how human behaviour influences them – particularly when we’re not around.

“We have huge expectations for our dogs: we expected them to be quiet and silent and leave us alone while we’re away from the house. Yet, the default setting for any puppy (and thus most domesticated adult dogs) is to scream like hell if they’re separated from the social group. In fact, as much as 80 per cent of domesticated dogs have a negative psychological reaction to being left alone,” she says.

“We’re failing our pets in this area. However, dogs are highly flexible species and can be taught from a young age that being left alone is okay. By leaving them very gradually for longer periods in a relaxed environment can help.”

How to stop a dog licking your face 

As Blackwell says, as long as you don’t have any open wounds, there’s no harm in letting your dog lick your face. However, understandably, some people aren’t thrilled to be covered in doggy drool.

Yet however unpleasant you find it, it’s important to avoid punishing your pet. “Some people may react badly and tell off their dog after they get licked. But this is unlikely to make the dog feel good – the licking is a greeting to them,” says Blackwell.

“Imagine if you tried to shake somebody’s hand and they slapped you away. You’d probably be quite hurt.”

The solution, instead, is to teach the dog an alternative greeting. “It’s all about positive reinforcement,” Blackwell explains.

“Cover your face with your hand and they’ll lick your hand instead – reward this behaviour and they’ll likely to target this same area next time.”

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Simply repeat this reward whenever your pooch licks your hand and eventually they’ll gift you with a greeting that doesn’t require a wet wipe afterwards.

About Dr Emily Blackwell
Dr Emily Blackwell is a Lecturer in animal behaviour and welfare at the University of Bristol. Much of her research focuses on why our animals behave the way they do – and how to improve their lives.

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