I have been on a "gluten-free" diet for a couple years now. This means that I have to carefully inspect the ingredients list of everything I eat, something that I didn't really do before. The results are unappetizing to say the least. Even worse, sometimes potentially harmful ingredients are not necessarily listed, or are listed by some rarely-known name.<p>If you wish to have good control over what you're eating, whether that means avoiding gluten, casein, animal products, soy, etc; your best bet is to prepare all of your own food. Don't eat out, don't buy preprepared foods at the market.<p>Disclaimer: I'm not quite disciplined enough to follow that advice, and I know that I end up eating small amounts of gluten. It's a trade off between stress and nutrition, I guess. Since vegans usually don't get sick by eating trace amounts of non-vegan food, my advice is to just deal with it. And be happy that you don't have a lot of real food allergies (unless you do, of course).