Milo suddenly hates Teddy?

Before I went to work this morning, Milo and Teddy were just fine with each other. I went down into my basement to get my laundry around 8:30 am and Teddy must have run down without me knowing. I came home around 3:15 and heard meowing. I let Teddy up and gave the both of them a can of cat food. However, as soon as they were done, Milo started hissing at Teddy. He smelled Teddy hissed again and started growling and batting at him. I thought maybe Teddy smelled too much like the basement and that's what was upsetting Milo so much so I gave Teddy a bath. Milo took one sniff and still kept hissing, growling, and putting his ears back. So then I took a towel, rubbed Milo to get his scent, and rubbed Teddy with it to transfer it. Still, Milo had the same reaction when he was near Teddy.

I don't understand. Milo isn't aggressive at ALL. Teddy is the dominant one. The two of them usually play and wrestle with each other. Milo behaving this way is so out of character. Teddy seems so confused why Milo seems to hate him so much after a 6 hour separation.


Just more info: Teddy is 1, Milo is 9 months old. Both are neutered indoor males.

Update: Milo walked up to Teddy again, who is sleeping in the corner, smelled him, and started hissing, growling, and hit him. Teddy did nothing!

The first two cats a got were brother and sister. Mo (the boy) got neutered first he was gone all day, when he got back Cinnie did the same thing that Milo is doing. She wasn't even close enough to get any smell off of him when she was looking at him like she saw a ghost and hissing and spitting. I know there was different scents on him, but it took a while for her to get back to normal with him. But it did happen. A Feliway Diffuser might help until then. It just takes time. Good luck. Keep us updated.

He's still having the same reaction to Teddy, although it seems when he is tired, he isn't as aggressive. I found him sleeping next to Teddy at the end of my bed this morning. It seemed like he was okay, but my boyfriend just called me and told me that Milo went back to last night's behavior. Milo even started going after my boyfriend when he picked him up.

Could Milo be sick, or is this just just a behavior issue? I'm so worried....

For some reason when some cats are upset they tend to strike out at the nearest living thing next to them. When my indoor boy Mo see's another cat outside, he starts going after one of my other cats thats nearest to him. It's only been a short time since that happened. It scared him for some reason being separated from Teddy. However, it wouldn't hurt to get him checked by a Vet in case something is bothering him. Also, if you can I have had luck with Feliway.

Stress causes illness in cats quite quickly. When they start getting sick, even before they are, their signature scent changes. It is a subtle change but cats pick up on it quickly. To Milo, that change means you brought another cat in the house. He doesn't recognize Ted. In your situation,I would be making a vet visit with Teddy. Being cut off all day in a basement sometimes isn't an adventure for a cat- it can and is stressful. I would make the appointment soon and have a full work-up done on Teddy. Good luck. In my book, better safe than sorry.

I created a new thread with an update in the Health section. I think Teddy got outside yesterday through a broken window in the basement.