That's the key right there. If you are unable to live a normal life, it's not everybody else's problem. We shouldn't have to accommodate everyone else.
If your kid is allergic to peanuts, why should the whole class have to not eat peanuts because of it? Maybe my kids favorite food is a PB&J?
(this post isn't directly at you Gina, just playing off your statement)
The necessary precautions would obviously depend upon the nature of their affliction. If they were allergic to something that might kill them, then I would probably recommend that they avoid the place that might contain that substance all together. If they are not able to avoid the place, then they should wear the necessary clothing, respirators, etc to make sure they are safe.