Why does a cat lick its face when it is not dirty?

A quick flick of the tongue over the lips is one of the tell-tale signs that a cat is becoming agitated, while at the same time being fascinated or puzzled by something. Keeping an eye firmly fixed on the source of its agitation, the cat gives the impression that it has suddenly and inexplicably developed an urgent need to clean its nose or the fur around its mouth. But there is no dirt there. The cleaning is not functional and it does not follow the usual pattern seen after feeding or during a normal grooming session. The licks are short and sharp rapid sweeps of the tongue that do not develop in the usual way into proper washing actions. They are the cat's equivalent of a man scratching his head when perplexed or irritated. Reactions of this type are called 'displacement activities'. They occur when the cat is thrown into a state of conflict. Something which upsets it but at the same time arouses its curiosity, will simultaneously repel and attract the animal.

There it sits, wanting to leave and wanting to stay. It stares at the irritant and, unable to resolve its conflict, shows its state of agitation by performing some trivial, abbreviated action – anything to break the stalemate in which it finds itself. Different species respond in different ways. Some animals nibble their paws, others scratch behind an ear with a hind leg. Birds wipe their beaks on a branch. Chimpanzees scratch their arms or their chins. But for felines the tongue-swipe is the favourite action. There is a harmless way in which this can be tested. Cats do not like vibrating noises with a high pitch, but they are intrigued by what makes such sounds. A coin rubbed back and forth along the teeth of an ordinary hair-comb produces such a noise. Almost every cat, when hearing the brrrrrr sound produced by this action, stares at the comb in your hand and then, after a few seconds, starts licking its lips. If the sound continues, the animal may eventually decide that it has had enough and it will get up and walk away.

Amazingly, this works for fully grown lions just as well as for small tabbies. Sometimes the lip-licking gives way to a violent sneeze, sometimes to a wide yawn. These actions appear to be alternative feline 'displacement activities', but they are less common than the liplicking. Why a cat is so irritated by a vibration sound is something of a mystery unless, during the course of feline evolution, it has come to represent a noxious animal of some kind – something unsuitable to attack as a prey. An obvious example that comes to mind here is the rattlesnake's rattle. Cats perhaps have an automatic alarm response to such animals and this may account for the fact that they are upset and yet intrigued at the same time.