So I have 2 cats that are around the same age. A Maine Coon (male) and a calico (female). They are like best friends. They follow each other all over, play together, etc.

I recently got the Maine Coon groomed for the first time ever. Just a shampoo, trim, and a fluff c:

He is acting like he normally does. My calico, however, has been hissing, growling, and attacking him since he got home from the groomers. He does not fight back. It's kind of sad to watch. He wants to play with her, and she's acting aggressive. I thought it would go away, but it's been about 4 days, and she's still acting this way towards him. Other cats in the house don't really care. It's just his calico friend acting up.

It must be the scent, yes? Any ideas of what I can do? I think she believes that he is an entirely different cat.

Someone said to put vanilla extract or something under each of their noses, but I don't know if that's safe to do. Do I need to give her a longer time to get used to his new scent/hairdo?

I've had cats for years, but this is the first time I've ever gotten one groomed. Will probably be the last T^T

I highly doubt the cat believes he is a different cat, unless your cat is blind. They do see colour and they would know the markings, looks, etc. It is likely the scent. Your cat now smells entirely different, including chemical shampoo scents, the lingering scents of sanitizers from the groomer, the people that touched your cat, the lingering scents of other animals around there. There is a lot to cling and it would be an attack on the senses.

Cats notoriously do not respond well to change. Consider it like this: your closest friend disappears, hours later returns and has a big makeover. You know it's them, but holy shit, what did you put on you? What did you do to your hair?

Vanilla could be a mistake for both of them if the scent is too strong. It's not going to neutralize the world around them, you could just piss everyone off and provide some feline headaches.

I would suggest giving it more time, and scenting up your cat. Take your Maine Coon and rub some dirty laundry all over that cat. Your calico trusts you and you are the common denominator, so put a familiar scent on your groomed cat and really put it all over. A vigorous rub down with a shirt of yours. Then take that shirt, and let the calico smell it because it will now have the MC scent on it. Maybe rub some toys on your MC. Bring them together with happiness and playful loving time. Make every inch of it an insanely positive experience. People take a similar approach to introducing new kittens by introducing scent and familiarizing the newbie.

Wow thank you! My calico is actually cross-eyed and blind in one eye. I'm sure she can see most of him though lol I guess I will start rubbing some dirty blankets and clothes on the MC. Thanks again for your advice! ^_^

Knowing her vision is poor I can imagine that would take an extra toll! Definitely try returning the scent to something familiar. It will get better probably as the perfumes wear off.

Yes, thinking about her vision problems; it makes a little more sense as to why she's being affected by it, and the other cats with normal vision in the house are not. I easily forget about her eyes, because cats are so good at adapting to things like that ^_^

It is some strong scented shampoo they used. It may take a while, so I'm going to try and be really patient with it c:

You could also try to rub your own scent on the maine coon so that he smells more familiar than shampoo to your calico. I suggest that if he has to be trimmed, ask that they don't wash him again with the scented shampoo. Cats wash themselves, so they don't really need baths, although I can imagine that maine coons can have some trouble with all that fluffy fur. I just give my cat a quick "bath" with a wet towel (not too cold) whenever it's too hot inside (he actually quite enjoys this, since he loves water).

You could indeed try what said. You could also rub some durty laundry over your calico and onto the maine coon to give him both your scent and the calico's.