What I've noticed anecdotally (feel free to critique this) is that of the few people I know who appear to fit that profile of having MCS, it's of my opinion that they would all benefit from stress-management techniques (including outdoor cardio exercise to help with breathing). I would suggest it to them if it weren't for the fact they're merely acquaintenances and not friends.

Of course, I don't mean to suggest that obnoxious use of perfumes should be encouraged, but for those who are extremely sensitive, it's perhaps worth a look given how rarely doctors seem to seriously prescribe exercise (I think part of the reason is that taking up a new form of exercise is intimidating and difficult to monitor for many people, and that not all doctors live the healthiest of lifestyles themselves).