If you want to stay out of the way when your kitty might be agitated and need to bite, then understanding their signs of aggression is key. Signs of aggression in kittens are similar to those in adults. So, if your kitty has dilated pupils and its ears are flattened and pointed backward on its head, they are likely feeling agitated.  If your cat has its tail stuck straight up in the air and the hairs on its back raised, these are pretty firm signs of aggression, too. At this point, it's recommended to stop what you’re doing and let your kitty have a cool-off period before play resumes.