Pesticides are often considered a necessary evil since many crops would be torn to shreds by bugs without them. Antibiotics are a key component of many pesticides, and at least one severe allergic reaction has been reported, with the possibility of many other milder responses flying under the radar. Pesticide-treated blueberries were the culprit in this case, but really any other fruit or veggie grown under such circumstances is a potential threat [source: MedlinePlus]. Of course, people with known allergies of any kind are always encouraged to carry an epinephrine pen just in case of accidental contact. Better safe than sorry!