It's possible this goes back to something your Mom made that you hated the smell of. I love cooking with onions, but from a distance hate the smell. Now, nausea and vomiting is going pretty far. Some people have weird food sensitivities -- some people eat dirt in a disease called Pica. You might also have some kind of sinus problem that affects your sense of smell, maybe heightening it -- most of our sense of taste is actually our sense of smell. But if you can find some connection to something that bothered you when you were young you'll have something to work on.