Catnip:

Canadian Catnip oil's main ingredient is Nepetalactone. Catnip is taken internally, usually as a tea, and the oil can be applied topically. Some people apply catnip directly to the skin for arthritis, hemorrhoids, and as a compress to relieve swelling. The nepetalactone however, is a volatile substance when applied to a porous surface such as skin, which allows air to oxidize it quickly (usually less than 30 minutes). Emulsification with the carrier oils, Ph balancing with L-Arginine, and the synergistic presence of evening primrose oil are all thought to slow the oxidization process.