I have two cats Whispurr is 11 and CT who is 4. When CT was introduced as a kitten Whispurr went mental!! She screeching, she growling, she hiss, her trail doubled in size, the hair on her back stood up, etc. I had to keep CT in the carrier for 2 nights because I feared whispurr would go after her! Eventually, Whispurr adjusted and after a couple of months they were getting along even eating out of the same bowl, even though they each had one. Fast forward 4 years. This morning I took Whispurr to the vet. They gave her an enema and I brought home later in the afternoon. But when she stepped out of the carrier CT went Mental and behaved just as Whispurr had when CT was introduced. I was just as fearful for my own safety today as I was when CT was introduced and Whispurr was acting out. Today CT looked at me with pure unbridled rage and looked as though she might become aggressive! Whispurr though disturbed remained quiet while CT continued to howl and hiss. The volume was truly astounding! I'm thinking CT smells the vet's office and treatment room and just no longer recognize Whispurr. As for me, I've been talking softly to her and holding my open hand out, which she, finally, moved toward and rubbed her face into, which is her habit. She remains, vigilant, in the other room and starts acting out whenever I re-enter the room, but I am able to calm her down now. Is this normal? How long will it last?