My cat always wants to bite my arm after I pet him for a while. Why does he do this?
There are two possible reasons your cat wants to nip at you after you pet him.
The first is that the extra attention puts him in a playful mood. Like a twitching string on a pole toy, your moving arm may stimulate your cat's need to work off some excess energy to play.
But the more likely explanation is that your cat is telling you, "Enough already!" He can't verbally communicate this message, aside from crying out, so he has to do whatever he can to get you to stop. It could be that you've made your cat uncomfortable in some way. Many cats are sensitive around the stomach area. They can tolerate a certain amount of massage there, but after a while, the pressure becomes uncomfortable for them. Be sensitive to literal sore spots on its body, as those can also signify health problems. A visit with your veterinarian can help you identify any such problems.
The good news about such unwanted friskiness is that cats almost always provide you with a visual warning before they bite. Watch your cat's tail: If it begins to swish from side to side, chances are he's had enough attention for now.