A pheromone is any chemical produced by a living organism that transmits a message to other members of the same species. There are alarm pheromones, food trail pheromones, sex pheromones, and many others. Their use among insects has been particularly well documented, although many vertebrates also communicate using pheromones. Their use by humans is controversial.
Insect pheromones of pest species, such as the Japanese beetle and the gypsy moth, can be used to trap them or to create confusion so that the pests do not lay eggs on crops.
In mammals and reptiles, pheromones may be detected by the vomeronasal organ, or Jacobson's organ, which lies between the nose and mouth, although some are detected by the nose.
Human pheromones
Pheromones are a popular device in fiction, including the novel Jitterbug Perfume by Tom Robbins and the film Love Potion Number Nine.
Some commercially-available substances are advertised using claims that the products contain sex pheromones and can act as an aphrodisiac. These claims often lack credence due to an excessive marketing of pheromones by unsolicited e-mail, and their effectiveness has not been demonstrated scientifically.
Nevertheless, a few well-controlled scientific studies have been published demonstrating that humans may use pheromones in some circumstances. The best-studied case involves the synchronization of menstrual cycles among women based on odor cues. Other studies have suggested that people can use odor cues to select mates who are not closely related to themselves.