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 of the opposite sex, 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.