Catnip drives about 75% of adult cats crazy, thanks to a chemical called nepetalactone. The kitties detect nepetalactone using their vomeronasal or Jacobson's organ. Catnip isn't just for cats, though. Human use catnip as a seasoning and in tea to relax, treat headaches, prevent hardening of the arteries, and reduce fever, among other uses. Insects use nepetalactone as a pheromone to communicate with each other. You can use it to repel roaches, kill flies, or even attract aphids to an unpleasant neighbor's rosebush.