Aggression

Has your cat suddenly started biting or scratching people?

Your cat shows threatening or harmful behavior — hissing, swatting, biting, scratching — directed at people, other cats, or other pets. Figuring out *which type* of aggression it is matters more than just noting that aggression happened, because the right response is completely different for each type.

Possible medical causes

Hyperthyroidism, arthritis, dental disease, and brain or neurological problems can all make a cat more irritable and prone to aggression
Pain-induced aggression: if a normally gentle cat suddenly bites, this is the first thing to suspect
Cognitive decline and sensory decline in senior cats can also make them anxious and prone to misjudging situations, leading to aggression

Possible behavioral causes

Play aggression: common in kittens or cats without enough playmates, who haven't learned to control the strength of their bite or claws
Fear/defensive aggression: a reactive response after encountering an unfamiliar person, animal, or sound
Petting-induced aggression: suddenly biting mid-pet and then jumping away, likely from overstimulation
Redirected aggression: a cat gets riled up by something it can't reach, and attacks a nearby person or cat instead
Status/social aggression: attempting to establish social standing, such as blocking a doorway or swatting at other cats
Territorial aggression: defending territory against a newly introduced cat or a stranger
Maternal aggression: a mother cat protecting her newborn kittens — a normal instinct
Idiopathic aggression: no clear trigger, with intense and persistent attacks — the most dangerous type, and professional veterinary behaviorist help is essential

Warning signs — see a vet right away

A normally gentle cat "suddenly" becomes aggressive (especially middle-aged to senior cats)
Aggression accompanied by an obvious pain response
The intensity of the attack stays high for a long time with no sign of calming down, or the attack has no obvious trigger
Bite or scratch wounds severe enough to bleed or require medical care

Initial at-home suggestions

Rule out medical problems first (especially thyroid, joints, and teeth)
Keep a record of "what happened in the 30 minutes before the attack" to identify trigger patterns
Watch for warning body language before an attack: dilated pupils, a swishing tail, ears pinned flat
Never use physical punishment or shout at your cat — this only increases fear and anxiety
In multi-cat households, if cats attack each other, don't use your hands to separate them — use a piece of cardboard or another barrier instead

Want to track this over time? Try Trucelo

Multi-cat conflict management — log incidents to find the root cause.

Coming soon — app in the works

Sources: Cornell Feline Health Center、ASPCA. For reference only — please consult a vet.