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I have two cats. They got along very well with each other and with me. One of them got sick recently and had to see the vet. He was gone for about two days.

He returned yesterday, and now the other cat won't stop hissing at either him or me. It's very annoying.

Can you tell me what the problem is?

this is a classic case of what is known as aggression trauma. It a strange behaviour which is difficult to explain. basically the cat is scared because of the changes and things that may have happened to the other cat at the vets. Plus they may smell different and this has triggered fear which in turn is reacted to aggressively.

the behaviour should subside in a few days but you can try and help by rubbing the cat that went to the vets with a towel which has been rubbed on the other cat. to transfer the smell.

If the behaviour is particularly severe you may have to follow the reintroduction procedure (described here /introducing-cats.html).

best wishes Kate


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Kate Tilmouth


I can answer most day to day cat problems encountered by owners. I have a good understanding of cat behaviour and problems which may arise from changes to their daily routine. I can advise on cat training including litter training and general day to day cat care issues. I am not a vet and therefore cannot answer medical questions.


I run my own cat website at and have been a dedicated cat owner for over 20 years. I have encountered many different cat problems and situations and feel that i have a good understanding of cats and cat ownership.

I am a platinum member of Ezinearticles where i write mainly cat related articles.

Educated to High School level and have since worked for many years in a customer support based environment, gaining vocational qualifications.

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