Cat Allergies Treatment

My roommate has two cats that make my allergies go haywire when they are roaming the apartment. When she puts them in her room, I am fine. However, lately we have only been letting one of the cats out. No allergies! Could I somehow be allergic to only the one cat?
The other cat has long hair and sheds more, while the one we let out doesn’t. He is also a male, while the long-hair cat is female. I have no idea if these things matter, but those are the major differences.