I've never been tested, but then I'm not an Olympic competitor! I don't know when testing becomes common. However, the US AntiDoping Agency has guides to prohibited substances for athletes. (800-233-0393) At quick glance, antihistamines, and NSAIDS-nonsteroidal antiinflammtories like Advil, Tylenol, etc. are okay. However, though natural supplements are not specifically banned, they warn that since the FDA does not test supplements, there is no guarantee the supplement isn't contaminated by something illegal. (there's examples of what they found in some supplements...like Prozac!) So you take them at your own risk of testing positive for something.

Additionally, keep in mind that natural calming supplements are banned for use in horses in competition. That includes valerian and chamomile, along with other herbals. The USEF has a list of banned substances for horses. You can email them at medequestrian@aol.com