Pheromones

Pheromones are a class of chemical substances produced and emitted by numerous species of animals (especially insects) and, apocryphally, by humans that influences the physiology or behavior of other animals of the same species (most often as a means of sexual stimulation).

Pheromones are external secretion that convey a chemical signal among organisms of the same species. Compare to hormones which are internal only to the organism but conveying a chemical signal among organs.

They are a popular device in fiction, including the novel Jitterbug Perfume by Tom Robbins and the film Love Potion Number Nine.

Some believe that certain commercially available pheromones can act as an aphrodisiac, but the beliefs often lack credence due to an excessive marketing of pheromones by unsolicited e-mail and their effectiveness is questionable.