My 12yr old indoor cat has suddenly started hissing at my 10yr old indoor cat. They have been together for 10yrs. The 12yr old just had a full exam at the Vet and all tests came back perfectly healthy. I did just move to a new apartment about 1 month ago - about the time the hissing started. They both seem to have adjusted and enjoy the new place. Could they still be adjusting and stressed out about the move?

It is possible that the 12yr old is still adjusting to the move. Did the prior tenant have a cat or another animal? It could be a strange smell is confusing the 12yr old. The 10yr old could also be sick. If it does not get better, or worse in the next week, you might want to take the 10yr old in for a check up too. You could also try felaway (sp?). It is a cat phermone that you plug into a wall outlet that will make kitty feel more relaxed. If you are on a lower floor, it could also be that the 12yr old is seeing other cats outside and is getting confused. The felaway could help with that too.

You are brilliant! Yes, the former tenant had a cat and I know there is a cat across the hallway from me. Most of the hissing seems to happen in the room that the former tenant had kept her litter box so that makes so much sense. Although everything has been swept and washed, I'm sure there is still a lingering scent. I am on the second floor and there are a lot of dogs as well as some outdoor cats that I have seen running around. I will definitely go buy the Felaway. Thank you so much for your advice! Yes, the 10yr old in scheduled for a checkup too :)

Glad to be of some help. I am no expert, but have had cats since I was younger. I currently have 5 of my own, so really it is just experience. If the felaway does not help anb/or if you want to rid the old cat box room of its smell, there is a product called Nature's Miracle. It has enzymes in it that eat up the organics that leave the smell behind.
You could try using that on the carpet or area where the old box was. However, over time,
Your cats smells should replace the old ones, and all should get back to normal. It might just take a little time. Also, the felaway plug in is about 25-35 dollars, so you might want to just try the spray version first. Spray in the AM and then again in the PM. If that does not work well, the plug in releases all day. Good Luck!

Hsk maybe right when I moved a few yrs back my cat was 7 now 11 he acted the same way except then we only had a dog. He would see the strange neighboorhood cats and go insane... he would try and attack anything that moved We had to keep the windows closed and keep him from sitting in them this was very hard as he is an indoor car. Our old street only had 1 other cat and he was 22, so not very much competetion there. But my old kitty has adjusted since I have a bigger home I bring it all kinds of stray's and he mostly accepts them now and seems happier. Good luck