Reading the warning signs
A cat rarely bites out of nowhere. Aggression is communication, and the warning usually comes seconds earlier: a lashing or thumping tail, ears turned sideways or flattened, wide pupils, skin rippling along the back, a stiff body, a low growl, or purring that suddenly stops. Many cats have a limit for how long they enjoy being stroked, and the bite that follows is often called petting aggression. The cat looked at your hand, tensed and twitched its tail first. Learn your cat's signals, stop before the limit, and always leave an exit so the cat can walk away instead of fighting. A cornered cat has no other option.
Play, fear, pain or redirected?
The cause decides the solution. Play aggression is typical of kittens and young cats: ambushes on feet, grabbing hands with soft bites and no hissing. It means the cat needs more structured play with wand toys and that hands are never used as toys. Fear aggression comes with hissing, crouching, flat ears and a blocked escape route, and the cat needs distance and fewer triggers. Pain is the first suspect when a gentle cat suddenly reacts to being touched in one spot or lifted, because arthritis, dental disease and hyperthyroidism all change temperament. Redirected aggression happens when a cat sees a rival through the window, cannot reach it and attacks the nearest person or housemate instead. Block the view and let everyone calm down.
What to do in the moment
If a cat grabs your hand, freeze. Pulling away triggers the grab reflex and makes the wounds worse, so go still, look away, wait for the grip to loosen and withdraw slowly. Never punish: shouting, water sprays or smacking teach the cat that you are dangerous and make the next bite more likely. Redirect instead by tossing a toy away from you. Separate fighting cats with a blanket, a cushion or a piece of cardboard, never with your hands. Take bites seriously. A cat's teeth leave deep puncture wounds that seal over bacteria, and infections are common. Wash the wound thoroughly and seek medical care the same day, especially for bites on the hand, for children and for anyone with a weakened immune system.
Making it happen less
Most aggression shrinks when the cat's needs are met. Play twice a day for ten to fifteen minutes with a wand toy and let the session end with a catch and a treat, so the hunting sequence is completed. Let the cat start contact, keep stroking sessions short and pause to see whether the cat asks for more. Give vertical space, hiding places and, in a multi-cat home, one more of every resource than there are cats: bowls, litter boxes, beds and scratching posts. Write down when the bites happen, because a pattern usually appears. Neutering lowers some forms of aggression, and after a serious cat fight a slow, step-by-step reintroduction works far better than hoping it blows over. Sudden change, escalation or injuries call for a vet visit first and then a feline behaviourist, and medication can support the training.