Ink or foreign material on my skin. This includes facepaint, ballpoint pen, fingerprinting, even dirt that gets under the skin in a bad scrape. Getting a needle or a skin test at the doctor's office is the worst (along with IVs). I get nauseous, weak and turn pale pale white if it isn't taken off immediately.
I can remember this happening as early as getting my booster shot before kindergarten (unfortunately one of my most vivid early memories). I haven't worn facepaint since first grade when I had to end trick-or-treating early to go home and take it off. Last time I got a shot, I had a new doctor and he didn't know this happened to me every time. He was so concerned I was going to faint that he made me lie down and sip water for 1/2 hour before I got color back!
The oddest occurrence: Cake frosting on my face in a food fight at a friend's sweet 16th made me feel ill in this manner. Second oddest: ashes on forehead every annual Ash Wednesday (Catholic).
Now NECEG might understand why I wash my hands obsessively if oil or grease gets on them when working on cars.