June 24, 2025, 1:48 pm | Read time: 5 minutes
“She attacked out of nowhere” is a phrase often heard when cats scratch or bite their owners. However, there are almost always good reasons for this behavior, and cats usually show clear signs beforehand that they are about to strike. PETBOOK editor and cat behavior expert Saskia Schneider reveals what these signs are.
One moment you’re cuddling closely, and suddenly the cat lashes out with its claws, seemingly attacking out of nowhere. This is likely why cats have often been attributed with traits like deceitfulness or unpredictability. However, in most cases, it’s a miscommunication. Many people don’t see or understand their cat’s subtle signals. In rare cases, there might be a serious problem behind it.
People Don’t See Signals
Cats “speak” with their bodies. But many of their warning signals are subtler than those of dogs–and are therefore easily overlooked. Sometimes it’s just a twitching tail tip or a slight flattening of the ears, signaling: “Thanks, I’ve had enough now.”
But even clearer signals, like suddenly stopping purring or abruptly turning and staring, are not interpreted by some people as signs to stop petting. If the cat is further pressured or touched in such moments, it feels compelled to be more explicit or to defend itself. To us humans, it seems as if the cat is attacking “out of nowhere.” For the animal, however, this is a logical reaction to previous signals that were ignored.1
Cat is Overstimulated
A common trigger for seemingly sudden attacks is overstimulation–for example, during petting. What starts pleasantly can suddenly become uncomfortable due to monotonous, repetitive touches. Many cats signal this with a slight tail wag, skin twitch, or tense body posture. If ignored, a short but intense attack often follows, accompanied by withdrawal. This behavior is also known in English as “petting-induced aggression.”
Behavior Tips:
- Keep petting sessions short and observe when your cat has had enough.
- Avoid petting the same spot for extended periods.
- Reward calm behavior with treats or friendly words–not excessive physical contact.
- Learn to accept your pet’s boundaries–affection should not be forced.
Territorial Aggression
A typical situation: The cat suddenly darts out from under the sofa and attacks the feet of its humans–or visitors. Cats are highly territorial. New housemates–whether human, animal, or baby–can be perceived as intruders. Even renovations, new furniture, or unfamiliar smells (such as from visitors) can disturb their sense of territory. Territorial aggression manifests through threatening gestures, attacks, or blocking access. However, we don’t always notice these threats because the cat is crouching under the sofa, or we might not even realize the animal is there and get too close.
Play Aggression
Especially young cats exhibit intense play behavior that can quickly seem threatening to humans. They stalk, jump, scratch, bite–all typical hunting and prey patterns practiced during play. Even during cuddling, cats can quickly switch to play mode and suddenly attack hands or feet. Unfortunately, many people unknowingly encourage this by playing with hands instead of toys. Redirecting to appropriate toys and immediately ending interaction when the cat shows unwanted attacks, scratches, or bites can help.
Behavior Tips:
- Use only toys–never hands or feet!
- Offer structured playtimes with hunting games (such as a wand toy) daily.
- End the interaction immediately if the cat gets too wild, and leave the room without comment if necessary.
- Provide various toys (with feathers, sounds, or food) to prevent boredom.
We’ve compiled more tips for proper play here: These 8 Mistakes Almost Everyone Makes When Playing with Their Cat.
Stress and Fear
Stress is one of the most common triggers for sudden aggression. It can arise from many factors: vet visits, loud noises, unfamiliar animals outside the window, or changes in daily life. If a cat sees no escape route, it may lash out in fear and panic–this is called defensive aggression. It’s always important to identify the stress trigger. It may be helpful to seek professional support from cat behavior therapists or veterinarians specializing in feline behavior.
Particularly tricky is the so-called redirected aggression: The cat is internally agitated by an unreachable stimulus (such as another tomcat outside)–and then suddenly attacks the person who happens to come too close.4
Behavior Tips:
- Provide safe retreats in stressful situations (such as elevated resting places or caves).
- Avoid picking up or pressuring the cat in such moments.
- Tools like pheromone sprays can help reduce stress.
- Gradually acclimate your cat to new stimuli through positive reinforcement (desensitization).
Illnesses
Sudden behavioral changes–including aggressive outbursts–can have medical causes. Pain from arthritis, dental issues, abscesses, or neurological disorders like epilepsy can lead a cat to suddenly attack–out of fear of touch or feeling threatened. Age-related cognitive decline, hormonal imbalances (such as thyroid issues), or infections can also influence behavior.
Rarely, a change in the brain can cause aggressive behavior without apparent triggers. In any case, sudden aggression is always a reason for a thorough vet visit.
When Should You Seek Help?
If a cat regularly or violently attacks, the behavior should be taken seriously–especially if injuries occur or the family’s daily life is affected. Besides medical clarification, a certified behavior therapist can help identify triggers and implement targeted countermeasures. Professional help is particularly important for redirected or idiopathic aggression (aggression without a clear trigger)–as such cats can become dangerous.
Why Your Cat Loves to Attack Feet: Understanding the Behavior
Cats Bite When Stroked for These 4 Reasons
This is what happens when the baby is suddenly attacked by the cat
Conclusion: A Cat Never Attacks Without Reason
Even if it may seem so at first glance–cats do not act aggressively without reason. Their behavior is often a reaction to overwhelm, fear, pain, or misunderstandings in living with humans. Those who learn to interpret a cat’s body language, respect its needs, and recognize potential triggers can prevent aggression early and restore harmony in cohabitation. Behind every seemingly “unprovoked attack” is a cat trying to express itself–and be heard.
About the Author
Dr. Saskia Schneider is a biologist with a Ph.D. During her studies at the Free University of Berlin, she focused primarily on zoology and animal behavior. In addition to training as an editor, she completed training as a behavior consultant specializing in cats.