I'm also allergic to penicillin, along with Keflex (cephalexin??) which is one of those that 10% of people allergic to penicillin are also allergic to. I don't know what happens to me with penicillin since I've been told ever since I can remember that I was allergic to it, I was given Keflex though in the military to "guard against" and ear infection when I managed to clog my ear up blowing my nose during hayfever season once. One pill resulted in a nice set of hives, thankfully that was all.
Anyway, I just started Humaworm this morning, no ill effects so far that would be related to an allergic reaction. I think it must be related to how pharmaceutical penicillin is processed and concentrated because I also recently learned that blue cheese (which I have eaten many many times without incident) the "blue" part is actually a penicillin bacteria.