Why are my cats suddenly fighting and hissing after a scary incident?

I am so sorry to hear about your kitties! I would recommend getting some Feliway multicat diffusers https://www.feliway.com/us/Products/FELIWAY-MultiCat-Diffuser which are a pheremone releasing product that can help these situations. A calming supplement such as Zylkene can also be helpful. Ensure the cats each have places they can hide/get away if needed as well as adequate numbers of litter boxes (one more than the number of cats in your household), water and food available where they can eat/drink without being disturbed by the other cat. If they are still fighting despite this, some training may be needed. You can read this article by a veterinary behaviorist for details on this: https://drsophiayin.com/blog/entry/feuding_felines/

I am sorry to hear about Memphis. Sometimes cats will react to a stressful situation by transferring their frustration/aggression to those nearby. I would be sure your kitty has a safe area at home where he feels like he can hide/get away if wanted and he can easily access his food/water/ and litterbox for the next few days. I would consider picking up a Feliway pheremone diffuser such as this one which releases pheremones which can be calming to anxious kitties. I would also consider a calming supplement such as Composure or Zylkene. Your vet may carry these or you can order them online or find them in some petstores https://www.petco.com/shop/en/petcostore/product/vetri-science-composure-feline-bite-sized-chews

If your cats have spent most of their time outdoors and now are spending time inside together then this change in environment could be causing tensions. If they are still outside all the time then it is possible that a new cat has come into the neighborhood and this has disrupted the social structure of the cats, or potentially one of the cats could be feeling unwell and therefore being more defensive, or they could feel they are having to compete for food/shelter. I would be sure both cats have equal access to food and water (they may need their own separate areas to eat/drink so they don't feel threatened) and litter boxes indoors. When indoors I would recommend the use of the Feliway Multicat diffuser https://www.amazon.com/CEVA-Animal-Health-D89410B-MultiCat/dp/B01AVHPFDS/ref=sr_1_4?ie=UTF8&qid=1503838561&sr=8-4&keywords=feliway+multicat, which is a pheremone product. I would consider an examination by your vet to look for underlying health problems as well.

Cats can keep up this stress type behavior sometimes for days. If she seems comfortable in your room then I would consider closing the door and keeping her safe if your room for a few days and then allow her access to the other areas in time. You can also use a product called feliway to decrease some of the tension. Best of luck and thank you for using Pet Coach.

Thanks for using Petco Pet Education Center, formerly Petcoach! This is possibly because she smells differently. I recommend a product called Feliway which can help decrease stress and anxiety associated with environmental changes and stressors. You may find this online or at your local pet store. It usually works great in this type of scenarios. Good luck and have a great day!

Hello. The biggest problem is trying to identify or understand what set Daisy off. Perhaps an odor or sound, or she may have sensed another cat outdoors that frightened her. Since it can be difficult to know, the best thing to do is be proactive. I would immediately purchase a couple of Feliway room diffusers & put them in the room the incident occurred, & any other rooms Daisy frequents. Feliway emits a cat appeasing pheromone which can calm a nervous kitty. You can buy these online or at most pet retailers. Start with this along with a good physical exam by your veterinarian. It is possible that she could have an underlying condition like arthritis or even a urinary tract infection that caused her significant pain. Hopefully, this will never happen again. Thanks for using Petco Pet Education Center, formerly Petcoach.

If the aggressiveness is only occurring after a bath I'd recommend separating them after bathing for a few hours until they have calmed. You can also try using a Feliway diffuser or spray to see if this helps reduce the tension. If the aggressiveness continues or gets worse you may want to schedule a vet visit to ensure Sasha is not having any health issues contributing to the behavior change. Thanks for using Petco Pet Education Center, formerly Petcoach!