Grooming changed behavior

we have two cats that have been together since they were kittens. they are now approx. 2 years old. We took one cat to get groomed and when we brought him back home the other cat reacted aggressively, by growling, hissing and swiping at him. They had gotten along wonderfully before this, what can we do about this situation? And why has the behavior chnaged? The groomed cat was a medium hair that had to be heavily trimmed because of mats, does the other cat not recognize him anymore?

Thanks in advance for any help.

Daniel & Linda

It's because the groomed cat smells different to the old one - all the shampoos, etc., and just the general different smell of the groomer's. Try wiping a towel on the groomed cat and then onto the other cat so they both smell more alike - it helps.