Aggressive biting frequently happens during a petting session, when the human buddy either doesn't read, or ignores the cat's obvious body language. Although some felines adore being petted for hours upon end, sometimes a cat will become over-stimulated for and will avoid petting sessions. Your cat will show her/his feelings with narrowed eyes, and flattened ears. If you wait for the foreseeable tail-lashing, you've waited too long, and you may be rewarded with a swift, hard bite. Watch out for the cat's signals and cease from whatever you're doing to thwart this behavior.
Your kitty may become distressed at seeing a strange cat outside the window, and react by attacking the first thing she/he sees be it another cat or you. This sort of behavior will necessitate creative thinking from you... Simply remove your cat to an area where she/he can't see the unknown cat. Then reassure kitty that he/she is top cat of the house. Spend a little extra time wither/ him with extra strokes, cuddles and a little interactive play. Perhaps a few treats will bring things back to normal
Medical causes should never be overlooked when new and abnormal behavior problems arise, counting aggressive biting and scratching. These could originate in undetected wounds, suffering from fleas or mites, or a hormonal imbalance. If a normally passive cat exhibits unexpected and mysterious aggressiveness toward you, particularly when being handled, a visit to your veterinarian is most certainly in order.
One of the most imperative duties a cat caregiver owes to her/his cat is to be aware of the feline’s common condition, both mental and physical, and to be sharp-eyed to any abrupt changes. This consciousness can be accomplished by habitually examining your cat so she/he is familiar to your touching every area of her/his body, from head to toe. Then, keep your eyes wide open for the warning signs of approaching aggression.
Close watch and intimate knowledge of your cat is the key.