Catnip is of Asiatic origin and contains a chemical called nepetalactone, which is present in its leaves and stems. This chemical has a very powerful effect on some cats. Catnip, a member of the mint family, is a harmless "high" for felines. Although many cats will eat it, scientists say they're reacting to the smell rather than the taste. Felines bite, chew, rub against, and roll in catnip to release the volatile oil trapped in the leaves.