My cat won't stop!

So I have 3 cats.

Two are siblings. I got them when they babies came thru animal control. I took them into foster and then adopted them.

WELL! I take the girl into get groomed yesterday. After bringing her home she was so terrified she hid under the bed.

I woke up this morning and she came out. However now her brother won't stop hissing at her. So much to the point that I petted him while he was eating and he growled at me, then swatted me!


What is up?

The likely explanation is that she no longer smells the same to her brother, and cats rely greatly on scents for identification. Her smell is mysterious and disturbing to him, so he is reacting negatively.

Possible solutions: A dab or two of vanilla extract at the base of their tails; rubbing corn starch powder into their coats; rubbing one cat with a towel and then rubbing the other cat with the same towel in an attempt to combine their scents. The goal is to get both of them to smell the same.

Even if you were to do nothing, once the female cat grooms herself extensively, thereby reestablishing her normal scent, things will be back to normal.