Petco Text Logo
Petco Pet Logo

  • Two Easy Ways to Start Earning Rewards!

Why is my cat aggressive after vet? Reintroduce in small apt?

Updated On September 23rd, 2025

Pet's info: Cat | American Shorthair | Female | spayed | 8 lbs

Our cat had 3 teeth extracted. Now our other cat has feline non recognition aggression and is hissing and growling at her. We live in a small 1 BR apt so we can't keep them in separate rooms. Cat 1 also had very bad breath because of her tooth problems, so her smell has changed significantly. I'm afraid they'll never get back to their former relationship where they slept together, bathed one another, etc. is there anything we can do? I'm afraid to leave them tomorrow when we go to work!

4 Answers

Most Helpful Answer

Image profile

Answered By Anna M., DVM

Veterinarian

Published on July 9th, 2017

Oh dear, how stressful! Unfortunately it can be common for cats to lash out when one cat in the household suddenly smells or acts different - as they tend to do when they come home from the vet. Most of the time they go back to their normal interactions once the strange smell (in this case, from the vet clinic) wears off and the cat relaxes and acts like herself....but in your case, there's nowhere for Tribble to hide and isolate herself while she readjusts to being home. The most important thing right now is to not allow them to fight or have negative interactions. As long as they can be kept separate while they both settle down, they will probably do ok - but if they continue hissing and growing, and worse yet if it escalates into a fight, that could permanently damage their relationship. I would absolutely keep them separate until they seem to be relaxing. I understand that'll be challenging in a 1 BR living space - but if possible, you could put 1 in the bathroom with her own litterbox & food, and then have them switch places tomorrow so they can get reacquainted with each other's smells. If that's not possible, you may need to crate them both while you work on their reintroduction. Perhaps you could borrow dog kennels so they can each have their own living space while they're confined. I know this isn't an easy answer - but the most important immediate intervention is to do what you need to do, to keep them from fighting while the stress levels come down! Finally, adding a pheromone diffuser such as Feliway Multicat may help promote a calming atmosphere. I hope this helps!

Vote icon

2Pet Parents found this answer helpful

Other Answers

  • Image profile

    Answered By Dr. Melanie, BVSc MS

    Veterinarian

    Published on January 12th, 2017

    The reason why is that Gizmo may smell differently after being separated. You can see this behavior when animals come back from the vet, as they smell differently. I would separate the cats, and slowly reintroduce them to each other. Take the cat who is aggressive, and put her in her own room with her own food, water, and litter box. Keep the door closed, and for a few days, feed them both treats on other side of door so they associate each other's smell with a good experience. Then let the other cat in the aggressive cat's room while the aggressive cat is in a cat carrier. They can smell each other, but not be in contact. If either becomes upset or show signs of aggression, remove the second cat from the room, and try again later. Praise them when they interact appropriately. When they are interacting well with each other through the carrier, you can let the aggressive cat out of her room, and see how she interacts with the other cat. Praise them when they interact appropriately, and separate them with any sign of aggression or upset. I would get a cat tree with lots of shelves to give the cats vertical space to get away from each other. I would keep the cat in her room when you go out until they are comfortable with each other.

    Vote icon

    1Pet Parents found this answer helpful

  • Image profile

    Answered By Dr. Melanie, BVSc MS

    Veterinarian

    Published on May 7th, 2020

    Thank you for contacting Petco Pet Education Center, formerly Petcoach with your question. Likely because one of your cats was at the vet, he smells differently so 2B views him as a stranger. leading to the aggression. I would separate the cats, and slowly reintroduce them to each other. Take 2B, and put him in his own room with his own food, water, and litter box. Keep the door closed, and for a few days, feed them both treats on other side of door so they associate each other's smell with a good experience. Then let the other cat in the aggressive cat's room while the aggressive cat is in a cat carrier. They can smell each other, but not be in contact. If either becomes upset or show signs of aggression, remove the second cat from the room, and try again later. Praise them when they interact appropriately. When they are interacting well with each other through the carrier, you can let the aggressive cat out of his room, and see how he interacts with the other cat. Praise them when they interact appropriately, and separate them with any sign of aggression or upset. I would get a cat tree with lots of shelves to give the cats vertical space to get away from each other. I would keep the cat in his room when you go out until they are comfortable with each other. I hope this helps!

    Vote icon

    1Pet Parents found this answer helpful

  • Image profile

    Answered By Dr. Melanie, BVSc MS

    Veterinarian

    Published on April 21st, 2018

    Great question! When a cat spends some time at the vet, they can return home smelling differently and that can lead to the aggression from the other cat in the home. I can give you a method to help get them along again. I would separate the cats, and slowly reintroduce them to each other. Take the cat who is aggressive, and put him in his own room with hs]us own food, water, and litter box. Keep the door closed, and for a few days, feed them both treats on other side of door so they associate each other's smell with a good experience. Then let the other cat in the aggressive cat's room while the aggressive cat is in a cat carrier. They can smell each other, but not be in contact. If either becomes upset or show signs of aggression, remove the second cat from the room, and try again later. Praise them when they interact appropriately. When they are interacting well with each other through the carrier, you can let the aggressive cat out of his room, and see how he interacts with the other cat. Praise them when they interact appropriately, and separate them with any sign of aggression or upset. I would get a cat tree with lots of shelves to give the cats vertical space to get away from each other. I would keep the cat in his room when you go out until they are comfortable with each other. Best of luck, I hope this helps!

    Vote icon

    1Pet Parents found this answer helpful

See More Answers

Related Questions

Petco Pet Education Center
New Pet
Why is my new pet biting? Is she stressed or scared in her new home?
New pet biting? A Licensed Vet Tech shares expert advice on how to gently acclimate your new companion to their home, reduce stress, and build trust. Get guidance for a happy pet.
Updated on December 04, 2025
Petco Pet Education Center
Health & Wellbeing
My pet is breathing hard, not eating, and lethargic. What's wrong?
Is your rat breathing heavily, won't eat, and has no energy? A Licensed Vet Tech explains potential causes like infection and age, urging a vet visit for diagnosis.
Updated on December 04, 2025
Petco Pet Education Center
Health & Wellbeing
My degu lost teeth after an accident. How can I feed him soft foods?
Your degu had an accident, lost teeth, and can't eat hard food. A Petco Vet Tech offers crucial advice on immediate vet care and how to feed your injured degu.
Updated on December 04, 2025
Petco Pet Education Center
Health & Wellbeing
My degu has trouble breathing, coughing, and nose discharge. Help?
Is your degu struggling to breathe, coughing, or have nasal discharge? A trusted vet offers vital guidance on respiratory issues like pneumonia and how to help.
Updated on December 04, 2025
Petco Pet Education Center
Health & Wellbeing
My rat is losing weight and has breathing issues. What should I do?
Dambo's weight loss, rough breathing, and mucus worry you? A Petco veterinarian addresses these concerning symptoms and recommends urgent professional care.
Updated on December 04, 2025
Petco Pet Education Center
Health & Wellbeing
How to keep a pet mom and her newborn babies warm and calm?
Support your pet mom and newborn babies! A certified vet offers advice on ideal room temperature, minimizing stress, and quiet intervention for food & water.
Updated on December 04, 2025
image
Have A Vet Question?

Book an appointment with the pros – our expert vets are here to help.

Book Now

Sponsored