Do Humans Use Pheromones?

                For ages there has been debate in the scientific community around whether the human animal utilizes pheromones.  Even for those who believe we do, there’s further debate about how powerful the effect is and what ways the pheromones are used.  For example:  Do we communicate to others our own psychological state and status through olfaction/pheromones?  Can we actually change each others’ emotional states or moods with pheromones?  Do we choose mating partners partially or sometimes completely from pheromonal cues? 

Women of reproductive age who spend a lot of time together have been documented to tend to menstruate near or at the same timeframe; many speculate a pheromonal mechanism for this phenomenon.   Women who are not on the birth control pill also prefer the body odor scents of men with major histocompatibility complexes (MHC) that are different form theirs; could this be a pheromonal mechanism to encourage healthy diversity in offspring and avoid inbreeding?

At the moment we’ve discovered some useful facts to fuel speculation.  For example, most or all humans do share the presence of the area in the nose that other primates use for pheromone detection, the vomeronasal organ (VNO).  The human VNO, however, doesn’t appear to have a designated area of the brain for processing its cues, nor afferent innervation for VNO pheromonal signals to travel through.  Additionally, many genes that are necessary for animal VNO functioning are simply absent in humans.  It has been speculated by Wysocki and Preti in 2004 that the olfactory epithelium itself, rather than the VNO may be able to respond to pheromones and send those cues to the central nervous system.  In other words, pheromones may exist and function in humans with or without a working VNO.

The human hypothalamus is definitely activated by two chemicals that are at least analogous to animal pheromones: andostradienone and estratetraenol.   Savic, Hedén-Blomqvist, Berglund, in 2009, set out to determine whether this activation happens via the VNO, veinous blood, or olfactory mucosa by testing the two chemicals on 12 adult men with nasal polyps.  The polyps physically blocked olfactory cues only, leaving the VNO and vienous blood unaffected.  They found that both chemicals failed to activate the hypothalami of the men with polyps, leading to the conclusion that the pheromones (or pheromone analogues, depending on your position in the debate) stimulate the hypothalamus via olfactory epithelium! 

See the study abstract here: http://www.ncbi.nlm.nih.gov/pubmed/19235878