I have a violent and severe allergy to lobster. I discovered it the first time I ate lobster, and it landed me in the hospital. I stupidly tried eating it again (I thought it might have been bad lobster or something, even tho no one else who ate that lobster got sick) and it landed me in the hospital again, worse than the first time. I had trouble breathing and severe gastritis and huge hives.
Ever after that, and finally taking to heart the lectures I received from physicians, I avoid lobster like the plague. I do not eat it, nor do I eat any kind of seafood salad that I am not absolutely sure does not contain any scraps of lobster, nor do I eat anything that might have suffered cross-contamination from lobster, or anything that is being served with the same utensils or from the same dish as lobster. I was warned by the physicians that the reactions would get worse each time and could do permanent or even fatal damage.