Aggression

Question
I have 2 cats they are brother and sister they have always gotten a long great untill he got sick and had to go to vet for a few days, he is home now and she is very aggressive to him what can I do?

Answer
Sue,

That is perfectly normal and typical behavior.

Cats go by smell and not by sight in recognizing other cats (with humans, they go by voice...not by sight). Your male cat brought home MANY different smells from the vet: anesthetic, medicinal smells, and smells of other cats...all clinging to his fur. The female cat thinks he's another cat! She is protecting her territory from this 'intruder'. Things will settle down in a few days when the smells are gone from him.

A trick that I've heard a lot of people use in that situation (though I have never tried it) is to put a drop of vanilla on each cats forehead so they smell the same.

I hope your kitty is feeling better.
Tabbi