My discovery that I was "allergic to penicillin" came when a Doc gave me a "synthetic" variety, Amoxycilin, that caused intense itching that just wouldn't quit. Althouth this wasn't "regular" penicillin, it apparently induced a rather generic allergy to the more common similar ones, with the result that since then I have to avoid all sourdough breads due to the very high percentage of them that use, or include, a yeast from the penicillin family. Fortunately, I never cared much for sour bread to begin with.

There are a few fungal infections, particularly in ceral grain products, that don't require you to be allergic to produce undesirable effects. Some fungi produces toxins (poisons) that affect anyone who ingests them. The classic example is the ergot smut that's fairly common in barley. It can infect wheat or corn products, but that seems to be extremely rare. The ergot toxin attacks the central nerve system, and can cause physical spasms and/or bizarre behavioural deviations before, fairly frequently, leading to death.

The death may occur as a direct result of the toxin, or as in the case of the "Salem Witch Trials" (perhaps) from the indirect reaction/action of superstitious neighbors to the characteristic symptomatic behaviour.

John