Cats do all kinds of stuff we don't understand — freaking out when they encounter a cucumber, for instance — but one sort of mystifying behavior they display is licking humans. Dogs have the reputation for being social, goofy and lacking a certain understanding of personal boundaries. Cats, on the other hand, are generally thought to be more standoffish and less prone to slobbering all over their human companions than dogs. But every once in a while, your cat will lose that sense of boundary and begin licking your face, your arm or some other body part with that scratchy tongue, begging the question, why?
Cats Are Mouthy Smellers
"Cats explore the world as kittens through their mouths and by chewing on things," Anita Kelsey, cat behaviorist and the author of Let's Talk About Cats, says in an email. "They lick to groom themselves and lick other cats — a behavior called 'allo-grooming' — in order to bond and groom."
Cats have a huge number of scent receptors compared with humans — about 200 million compared to our measly 5 million — so scent plays a big part in their everyday lives. Cats can smell in two different ways. First, they sniff through their noses in short, fast inhalations that capture the scent molecules and hold them in a chamber in their nasal cavity to let all their scent receptors do their work. Second, cats can taste and analyze scent through an organ on the roof of their mouth called the Jacobson's organ, or vomeronasal organ. When they're using their Jacobson's organ, they make a weird face — sort of an open-mouthed grimace that scientists call a flehmen response.
Cats Sometimes Lick Because They Like You
Because most of a cat's face is involved in the activity of smelling, it makes sense that a cat would lick you in order to get more information about you. But more than that, cats lick who they like.
"Cats lick us as a sign of closeness, bonding and affection," says Kelsey. "It's a form of grooming us as they do with other cats they have bonded with. I am sure they are also enjoying taking in our scent. They love armpits, for example, as there is a strong scent there."
Although cats aren't as exuberant in their demonstration of affections as dogs can be, according to Kelsey, we shouldn't compare the two animals.
"We are seen as part of the cat family," says Kelsey. "Cats show us affection through behaviors like remaining in our company, purring, sleeping next to us and on our laps, and rubbing against us."
Territory, Terror and Taste
Aside from a cat's general affection for you and the urge to groom a buddy, a cat might lick you for a variety of other reasons. For starters, if your cat is regularly coming at you with its sandpaper tongue, the reason might be that it wants to mark you as its territory. And what better way to tell other cats to back off than by smearing you with a little special spit perfume?
Cats also tend to lick things they think are tasty. Cats cannot taste sweet things (they're the only mammal that can't), but they might really like your hand lotion or the residue that breakfast left on your fingers. If you find your cat is particularly interested in a specific cosmetic product or ointment you use — especially a prescription ointment like a hormone cream — ask your vet whether it's safe for them to ingest.
Some cats also lick in order to cope with stress or fear. This behavior is especially common in cats who were taken away from their mothers very early, but it can happen in any cat. If this behavior seems to worsen over time or is accompanied by nervous body language, or if they begin over grooming themselves to the point of creating bald spots, it's a good idea to ask your vet about treatment.
How Much Licking Is Too Much?
It's very sweet that your cat likes you, wants to keep you clean, wants to tell other cats you're their person, but sometimes the licking can get to be too much. Especially because those little keratin barbs on their tongue (called papillae) can really hurt!
To dissuade your cat from licking you, you can try distracting them with a toy, getting out a brush and grooming them, simply walking away, or even just putting a cardboard box in the middle of the floor — it's worth a shot!