OK. That’s what I wanted to hear.
Tell them nicely and politely to please stop....use words like please, sir, madam, excuse me.
If that doesn’t work than annoy them right back by singing show tunes off key until they can’t take any more and agree to stop.
Try it sometime. Pretend that you're sensitive to some substance and ask the offending person to change and see what kind of response you get.
Most take it as a personal insult. Instead of *Oh, I didn't realize that it was harming you.* all you get is, *You can't tell me what to do. I have my rights.*
The courteous are few and very far between, and likely to have reactions themselves.
Only someone who has similar problems can understand the hell someone else's actions can make a life.