Some Orionfemales secreted a highly potent pheromone that accelerated the metabolisms of males of many species, raising adrenaline production to dangerous levels. It caused aggression and a form of delusion that made the males susceptible to suggestion. The pheromone caused headaches in Human females and disrupted the sleep cycle of Denobulan males; Vulcans, however, were immune. The pheromone's effects were cumulative; the longer one was exposed, the more pronounced the results. In 2154, DoctorPhlox of the Enterprise NX-01 theorized that the pheromone acted as a defense mechanism against competition. (ENT: "Bound") Not all Orion females chose to secrete these pheromones. (LD: "We'll Always Have Tom Paris")
In the stage directions from the first draft script of ENT: "Rogue Planet", Captain Archer likened a form of chemical signature emitted by wraiths, when they were afraid, to a pheromone and, shortly afterwards, called the chemical actually a pheromone. However, these two references weren't included in the final draft of the teleplay (nor in the final version of the episode), in which Archer's likeness was omitted altogether whereas, in the second reference, the term "pheromone" was replaced with the word "chemical".