Human Pheromone Reviews
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How Pheromones Work - Part 1
In addition to our sense of smell, we have the ability to sense certain chemical signals emitted by people around us—without being aware of it. Scientists are only just beginning to uncover our alternate way of "smelling."
A whiff of airborne chemicals from a female mouse, for instance, may spur a male mouse to mate immediately. Certain chemical messages from other males may make him aggressive. Other messages may produce changes in his physiology—as well as in that of the responding female.
The effects of such messages would be far less obvious in humans. When we receive chemical signals from people in our vicinity, these signals must compete with many other factors that influence our behavior. Yet our physiology may be just as responsive to chemical messages as that of other mammals. It is known that certain chemical messages from other mice lead to the onset of puberty in young males, while a different set of signals brings young female mice into estrus. Similarly, there are some suggestions that women may alter their hormonal cycles when exposed to chemical signals from other people.
In the past five years, scientists have become extremely interested in these signals, as well as in the "accessory olfactory system" that responds to them in many animals. This system starts with nerve cells in a pair of tiny, cigar-shaped sacs called the vomeronasal organs (VNOs), where the signals are first picked up. The VNO appears to be a much more primitive structure that uses a different set of molecular machinery than the main olfactory system .
The VNOs are located just behind the nostrils, in the nose's dividing wall (they take their name from the vomer bone, where the nasal septum meets the hard palate). In rodents, at least, signals travel from the VNO to the accessory olfactory bulb (rather than to the main olfactory bulb) and then, to parts of the brain that control reproduction and maternal behavior. It's an alternate route to the brain. If the accessory olfactory system functions in humans as it does in rodents, bypassing the cerebral cortex , there is likely to be no conscious awareness of it at all.