Anaphylaxis is serious shit.
I've had one episode, when taking penicillin. Had had no problem with penicillin my entire life, and then one day in my 30s I was taking some for a respiratory infection and I blew up like the michelin man - couldn't breathe, etc. Quick trip to the ER saved my life. On visiting my doctor, he said "that's it, next time you have penicillin it will kill you.
Apparently you can "develop" an allergy to some things late in life - you'll be fine, and then all of a sudden one day your body will say "okay, that's enough of that" and you can't ever have it again. Scary thing is, my doctor said it happens with all kinds of things, like... strawberries.
Not sure that life is still worth living if, someday, my body decides I can't have strawberries any more...
I've definitely become more allergic to bites/stings from wasps etc, never had a problem until I was about 20 and then suddenly a sting from some type of mosquitoes on my lip and that was it. Out cold in 20 minutes and I'd never even heard of anaphylactic shock before that.
Does make you think twice about the holiday destination.