Sibling kitten returned from vet visit

Question
We recently adopted 3 female kittens who are extremely loving and playful with no rivalry.  However, this weekend one of the sisters got hit by a car and spent 2 days at the vet.  She is fortunately ok, only sustaining some fractured ribs and contusions, but she spent 24 hrs in ICU and in an oxygen room.  We took her home last night and now her 2 sisters are hissing and treating her like a stranger.  What happened in the 36 hrs that she was away to make the other two dislike her?  Many thanks for your insight.
Kathy

Answer
Kathy,

I'm glad your kitty is OK! Unfortunately when you have cats things can happen, even to house cats.

Your other cat's behavior is normal for a lot of cats after one comes home from the vet or animal hospital.

Cats go by smell and not by sight in recognizing other cats (with humans, they go by voice...not by sight#. Your cat that was at the vet brought home MANY different smells: anesthetic, medicinal smells, and smells of other cats, etc....all clinging to her fur and skin. The other cats thinks she's another cat because she doesn't smell the same!

When the hurt cat grooms herself she will be replacing her regular scent. You can also rub the cats who did not go to the vet with a towel, then rub the cat who did go to the vet with the same towel to transfer familiar smells, but do not do it the opposite way because you will then be transferring the vet's office smells to the other cats.

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.

Things will settle down when the smells are gone from the female that was at the vet.

Tabbi