Cats bite for quite different reasons, and the fix depends entirely on which reason you are dealing with. The first thing to establish is whether the cat is playing, is overstimulated, or is in pain.

Play biting

Most common in kittens and in cats that were hand raised or homed too early. Kittens learn bite inhibition from their littermates; a kitten that grew up without that lesson bites too hard without understanding it.

The typical picture: the cat stalks, pounces on ankles and hands, grips with the front paws and rakes with the back ones. There is no growling and no flattened ears. This is hunting behaviour with nowhere to go.

The fix is not punishment. It is redirection:

Never use hands or feet as toys. Not once, not with a kitten.
Use a wand toy so the target is at a distance from your body.
Play properly twice a day, in the hunting sequence: stalk, chase, catch, and then a meal. Ending play with food completes the sequence and settles the cat.
When teeth touch skin, stop moving, get up and leave the room. Ending the game is the consequence that teaches.

Petting induced aggression

This is the cat that enjoys being stroked, then suddenly turns and bites. It is not treachery; it is overstimulation, and the cat almost always warned you.

The warnings come in order: the tail begins to flick or thump, the skin along the back twitches, the ears rotate back or flatten, the body stiffens, the head turns towards your hand.

Stop at the first sign. Keep sessions short, favour the head and cheeks over the back and belly, and let the cat come to you.

Pain

A cat that has recently started biting when handled, or when touched in one particular place, is very likely in pain. Arthritis, dental disease, ear infection, and injuries are the common causes.

Sudden onset aggression in a previously gentle cat is a medical sign, not a behavioural one, and it deserves an examination.

Fear and redirected aggression

A frightened cat that cannot escape will bite. Give it a route out and somewhere high to retreat to; never corner it.

Redirected aggression is the cat that sees another cat through the window, becomes highly aroused, and attacks whoever is nearest. It looks unprovoked and is not. Block the view, and leave the cat alone in a quiet room until it settles, which can take hours.

Cat bites need medical attention

A cat’s teeth are fine and sharp; they inject bacteria deep and the skin closes over the top. Cat bites to people become infected far more often than dog bites. Wash a bite with soap and water and see a doctor, particularly for bites to the hand.

When to come in

Any cat whose biting has recently started or increased. Any cat that bites when a specific area is touched. And any bite that has broken your skin.