Hiya Cracker Monster!
Sorry to hear about the no more peanut butter and crackers thing...bummer!
O.K., barring a person, being one of those with a genetic disposition and renders them allergic to almost all foods, then my answer would be no. Those type of people are a very rare type that you just don't run into. Your body requires food to exist, and it pretty much is hard wired to accept that fact and would accommodate just about any agreeable food item. Of course there are exceptions to this being allergies, but I have yet to hear of a person that developed allergies as the grew that made all food dangerous to them; now I'm not saying there is no such person, but the likely hood of that happening is nil to none. I hope this helped, good luck.
