Cat attacked my other cat randomly

Question
I have a neutered male that is 2.5 years old and a sterile female (I've been to the vet and she just has never been in heat, a kitten illness is suspect) 1.5 year old. They have lived together for over a year. When we first got her, our male became maternal and adopted her. They slept together, groomed each other, played together, etc. Two days ago we gave our male a bath after he played in the litter box and smelled really bad afterwards. We used the same stuff we always use to bathe both of them (although we don't do it often, they both have been bathed before a few times). We have never before had problems. Then, two days ago after the bath the female started to attack the male. Out of nowhere she started clawing him, growling, meowing weirdly, etc. The male just sat there calmly but I could see he was scared and confused. We put her in a separate room with her own litter, water, and food. We have tried taking her out every few hours but she still exhibits the same behavior. I don't know what to do. Just two days ago they were grooming each other and now we can't have them in the same room. I need help...

Answer
Agnes,

Don't panic! That is a common reaction and problem that comes up.

Cats go by smell and not by sight in recognizing other cats. (With people it is voices they recognize, not sight). Since you gave your male a bath, he smells different to her, therefore she probably thinks he is another cat and is defending her territory from this 'interloper'.

when the male grooms himself he will be replacing his regular scent. You can also rub the female with a towel, then rub the male with the same towel to transfer familiar smells. Do not do it the opposite way.

A trick that I've heard a lot of people use in that situation (though I have never tried it) is to put a tiny drop of vanilla on each cat's forehead so they smell the same.

You can separate them for a couple days if you think it is necessary, but things will settle down in a few days when the smells are gone from male and he smells like himself again.

You can also try giving the cats a special kitty treat that is strong smelling, like tuna or tinned sardines in oil. You can try one plate or one next to the other. That way they will associate each other with something pleasant instead of negative.

Tabbi

Tabbi