Add sunscreen to that list as well. I was briefly detained for that when I was coming back from Hawaii. I'd gone to the beach the day before, and used the same jeans, leaving trace amounts of residue.

Really, there are a ton of false-positive substances that we use every day. We need to realize that a false positive can happen to anyone, regardless of their background or morals, and we should treat suspects (for lack of a better word) with respect.