My cats are fighting to the extreme

Question
A few days ago both my cats, who are spayed and sisters, were laying in the window together and all of a sudden they just went at it! I think there may have been another cat outside. They started to fight, hiss, scratch and continue to fight til I was able to break them apart. It was pretty serious because one of them was bleeding form her ear. It has been about 5 days and they still hate each other and if they see each other, they hiss and I break it up before anything starts. What can I do to end this feud? I have cat sedatives that I used when I traveled with them, could I use them to make this process go smoother? Thanks for the help!!

Answer
Hi
this is not a uncommon problem is known as aggression trauma. basically they have become afraid of something, like seeing another cat and are taking their fear out on each other even though the other cat was not the cause of the fear. it is a very strange behaviour but i do get asked about this issue a lot.

basically what you have to do is to help your cats calm down and rebuild their confidence in each other again. this is best done using the introduction method, it does take some time and patience but is worth it in the end.

The process is described here on my web page

/introducing-cats.html

best wishes Kate