Pheromones are essentially chemical messengers released by animals that affect other animals. Usually they serve to communicate something about territory, reproduction and caring of offspring, the presence of danger, or even the presence of a rival. All animals from insects to humans have pheromones and they have a powerful effect on behavior. Pheromones have even been classified based on their uses into three classes:

Primer pheromones shift the hormonal balance in the receiver; releaser pheromones produce specific behavior patterns like avoidance or attraction; finally, information pheromones convey information about the producer to the receiver, including health, fertility, et cetera.

Human pheromones are continuously studied by scientists in an effort to understand the extent to which they affect us. Some scientists claim that the organ responsible for detecting pheromones in most mammals, the vomeronasal organ, is almost nonexistent in humans and that we have evolved to the point where humans no longer use these chemical odor signals. Other scientists dispute this with evidence from experiments that human pheromones have a powerful effect on other humans and can change the ovulation cycle of women and perceived attractiveness of potential mates. Experiments using male sweat have shown that human females react to male pheromones by increasing their fertile cycles and delaying the onset of menopause.

Synthesized human pheromones like androstenedione and estratetraenol, used topically, have been studied and shown to significantly increase the frequency of sociosexual behavior in participants using the pheromones as opposed to the placebo. These results have helped launch a variety of products claiming to have a put a ""pheromone to attract women"" in a bottle or vice versa. Some of these products are undoubtedly simply fragrant water, but others that actually contain synthesized pheromones have been purported to work effectively. The caveat seems to be that their effects are dependent on psychological and social factors that also strongly influence human behavior. Perhaps the confidence boost that pheromone wearers have is what makes them seem more attractive to potential mates, not the chemicals themselves.

The debate over the extent to which human pheromones affect human behavior continues, and like many scientific puzzles, studies seem to contradict each other. Moreover, human behavior, a thing affected by a variety of factors, does not lend itself easily scientific studies easily.