I've had chest infections in the past, and the doctor has told me it's viral, and then that he's going to prescribe me some antibiotics. Wait... what? "It won't cure it, but it might help you get over it" or something along those lines was his attitude.
So after getting prescribed antibiotics a few times for various things, I then developed an allergy to penicillin and my face went numb and my lip welled up during a course of treatment. Well, that's just great that is. Now I am screwed should I ever catch a real disease and need such things, although as I'm a dairy farmer my immune system is pretty good comparably.
I think I'm allergic to something else too which I haven't figured out yet, just my lip goes a little numb from time to time. Maybe just the traces of anti-biotics in my day to day diet...