- Medical issues are medical issues, not things to negotiate about. If you insist on bringing scented products into our college dorm room I will have the RA make you throw them away. Ditto with perfumed body stuff - if I tell you to not bathe your hair in highly scented hairspray in our room, just do it. I'm not "being difficult," I'm trying to breathe, and again I will tell the housing people to make you move.
In a college dorm situation, there should be a way for a roommate to say that they can't accommodate your disability and ask to be moved. However, most of the colleges I know have a very strict policy of making roommates work out disagreements, and for something like this, they might not let the non-allergic person move.
If someone really likes scented products, they should have the opportunity to say that they can't really live with someone who is allergic to them. Same with someone who loves peanut butter, when paired with someone who is allergic to it.
A dorm room is home for 8-9 months of the year. A random roommate should not be forced to accommodate an allergy or disability without having the chance to know about the accommodations beforehand and have a chance to think about whether or not they can deal with the changes required. It's a safety issue for the allergic person--someone who is forced to use/not use something against their will is far more likely to forget and use the forbidden substance, or not realize a common product has that substance in it.
A friend of mine has a guide dog. Her university gave her a roommate who was very, very afraid of dogs and who could not deal with a large German Shepherd Dog in her dorm room. The university followed its standard policy of making the two of them live together for a month before letting the roommate move into another room. During that month, the two women never actually were in the room at the same time, because of the dog. They stayed with friends and alternated who got to use their room and when.
It would have made a ton more sense to let the roommate know about the dog before she moved in, and then taken steps to find a roommate who liked dogs. My friend was assigned a triple room, but with only one other person, so there was more space than in the average dorm room, so there were compensations.
For the scented product user, it's a big change to not use scented products for 8 months or so--and expensive, if she'd come to college with scented lotion, deodorant, shampoo, conditioner, laundry detergent, fabric softener, etc. While she certainly should not have been using them around you, there should have been a system in place for the two of you to easily part company and find new rooms/roommates.
I don't think forcing someone to accommodate another person's allergy in their own living space is fair to either party. The allergic person has to worry all the time if the roommate will forget and use/eat the allergen, and the other person has to make huge changes in their lifestyle that they didn't ask for and weren't warned about. It's one thing to not be about to eat peanut butter in a classroom; it's another to completely change nearly every personal care product you use for months on end, without prior warning.
I blame the college or university for this sort of thing. They need to have a better policy to deal with roommate issues like this.