After a medical condition is ruled out, the next most common reason cats engage in unwanted behaviors is stress. Things can cause stress in cats that humans may not understand, like: A change in an owner's schedule. A new pet or person in the home.

What to do when your cat is acting out?

If your cat is not acting out because of an injury or illness, it's time for some training. If you've been play-fighting with your cat, stop - it encourages aggressive behavior toward you. Let your cat play rough with a toy she can chase instead. If she nips at you during play or petting, stop and walk away.

What causes a cat to act out?

A cat that is not normally prey-driven and is hissing, swatting, biting, and overall aggressive towards other pets and/or people is probably trying to tell you something. Pain and fear are often the reasons for a cat to have a behavior change that results in aggression.