Human sex pheromones
No study has led to the isolation of true human sex pheromones, though various researchers have investigated the possibility of their existence. Sex pheromones are chemical (olfactory) signals, pheromones, released by an organism to attract an individual, encourage it to mate with it, or perform some other function closely related with sexual reproduction. While humans are highly dependent upon visual cues, when in proximity, smells also play a role in sociosexual behaviors. An inherent difficulty in studying human pheromones is the need for cleanliness and odorlessness in human participants. Experiments have focused on three classes of putative human pheromones: axillary steroids, vaginal aliphatic acids, and stimulators of the vomeronasal organ. Axillary steroids are produced by the testes, ovaries, apocrine glands and adrenal glands. These chemicals are not biologically active until puberty when sex steroids influence their activity. The activity change during puberty suggest that humans communicate through odors. Several axillary steroids have been described as possible human pheromones: androstadienol, androstadienone, androstenone, androstenol, and androsterone. Androstenol is the putative female pheromone. In a 1978 study by Kirk-Smith, people wearing surgical masks treated with androstenol or untreated were shown pictures of people, animals and buildings and asked to rate the pictures on