No one likes additives. For most people, it's just a weird bunch of words that sound vaguely science-y and are printed on the back of whatever they're eating at the moment. But for some, mainly those with allergies, additives must be watched and looked out for.
Not all of these chemicals are terrible for you, however, and quite a few still come from natural sources.
Some of the strangest additives, such as crushed beetles or sheep juice, are collected into a nice list just after the link.