Have any of you found out you were allergic to something after years of not knowing?

About three years ago, I was talking with some friends at work, about how much I like mushrooms but they're too spicy. They looked at me like I was crazy! Turns out, I'm allergic to them. On a side note, my doctor told me that in a lot of cases, heartburn can be an allergic reaction to certain foods. For example, peanuts give me heartburn.