Sudden Aggression between cats? Does Feliway Help?

A little over a year ago, we adopted Orpheus from the SPCA, and he's always been a sweet cat without an aggressive bone in his body. However, over the weekend something happened with the cats and now they are not getting along with each other. They were cuddling together in one of their cat beds under the table when we went to bed Friday, and we were woke up to the sound of an awful cat fight about an hour before their breakfast. We ran downstairs to find tufts of Orpheus's fur all over the kitchen, and the two of them were going at it and Bandit had peed all over the kitchen floor.

Ever since then, things have been very tense between the cats. We had to separate them for long stretches over the weekend. They take their meals together just fine, no hissing or posturing or bad body language, but outside of meals or treats Bandit hisses at Orpheus if he comes near him most (but not all) the time. Sometimes Orpheus responds to Bandit's hissing as he always has, by ignoring it and being his normal sweet self, but he's also at times starting growling an yowling at Bandit and escalating the aggression (and he's never behaved this way before). Last night, they curled up and slept together again like nothing was wrong. Today, Bandit's hissing at Orpheus again. I'm very confused at this turn of events and I have no idea what caused it. I also don't know what caused Orpheus to randomly act so aggressive towards Bandit, when he's not been the least bit aggressive
the entire time he's been with us. I've been freaking out every time I see Orpheus approach Bandit because I don't know if he's approaching to attack him or try to cuddle and groom him.

I ordered a Feliway Multicat Diffuser on Amazon today. Has anyone used this with any success with their cats? I'm scared to leave them alone in the house together now, so I've been shutting Orpheus in the bedroom when no one is home. I feel really bad doing this, and I'd like to get things back to normal with them as quickly as possible.

 

Maybe something is wrong with Orpheus, one of my civies had been very aggressive all the sudden, then I noticed she kept scratching her chin, I looked in her mouth and even though she had a dental in September it was very obvious she had an abcessed lower incisor, I called for some antibiotics last Monday and then took her in on Friday and had it pulled and another dental done and her aggressiveness is gone. If possible I would check to see if Orpheus does have some sort of problem that could be causing him pain.

 

Another thought...could there have been a stray cat that's been hanging around your house? Perhaps Orpheus or Bandit are displaying displaced aggression because they can see or even smell the "intruder?" I know male cats wandering our neighborhood love to spray our front door all the time. That scent can definitely be picked up even if your cats are indoor-only.

I've used Feliway for this and other similar situations...it does seem to take the edge off. With seven cats in our house, it's pretty much inevitable that disagreements will occur, so Feliway has come to the rescue many times.

 

I use Feliaway and it can help take the edge off the aggression. But you probably need to get to the cause. Has anything changed in the house recently? Something that might cause some territorial problems? Does it usually happen in the same room? Both Nancy and Scotty and LaraB have good ideas. A trip to the vet may be in order if this keeps up.

 

Orpheus already has a vet appointment scheduled for next Tuesday so he will get checked out. There aren't any strays around us, but we did have new neighbors move in about a month ago. I don't think they have cats...if they do I haven't seen them. The new neighbors are kind of loud and argue a lot, but it hasn't seemed to bother him before. I'm just baffled.