9. Jeans — or any pants that have a rivet button clasp: Because this hardware tends to contain nickel, one of the most common skin irritants, it could trigger a rash just below your belly button, Dr. Zeichner says. If you've ever reacted this way, there's an easy fix: Just paint the rivet with clear nail polish or iron on a small patch. Either solution will provide a barrier between the metal and your skin.