The Medicine Cabinet: Ask the Harvard Experts
By Robert H. Shmerling, M.D.
Q: I haven’t yet picked a Valentine’s Day gift for my girlfriend. I was thinking about a pheromone-containing perfume. Do they really work?
A: Experts don’t agree on whether pheromones exist in humans, and whether they influence our behavior. However, it has been documented that some animals do communicate through chemical signals.
A male moth, for example, seems to sense the presence of a distant fertile female and will drop what he’s doing to mate. Sea urchins use “chemical attractants” as well. They release substances into the water that tell other urchins it’s time to reproduce. The insect and animal kingdoms are teeming with similar stories.
Several studies — mostly small and uncontrolled — suggest that the smells of certain chemicals can influence human sexual behavior in humans, too.
For example, one study tested the effect of a pheromone added to the usual perfume of 36 single women. None of the women knew whether she had the “sexual attractant” or placebo pheromone in her perfume. Both were odorless.
After 14 weeks, 74 percent of the women who had the pheromone reported an increase in sexual behaviors (including frequency of dating, kissing, sexual intercourse and sleeping next to their partners). Only 23 percent of those who had the placebo reported this type of increase. We don’t know, however, how much of the increased sexual behaviors were actually due to pheromones rather than something else.
Another study found that men who smelled clothing worn by a fertile woman drank more beer than those who smelled clothing from a non-fertile woman. So, it’s possible that pheromones might affect many behaviors; not just sexual behavior.
Another difficulty in understanding the impact of pheromones on human behavior is that there are literally hundreds of potential pheromones. The exact chemical make-up and action of all of them are still a mystery. So we can’t yet single out the one — if there is one — that influences sexual behavior or interest.
Plus, it’s not clear how humans sense pheromones, if we do at all. Animals that clearly respond to pheromones have a specialized nerve cell in the nose, called the “vomeronasal organ.” It is separate from odor detection.
Some researchers believe that tiny crevices in the human nose act as vomeronasal organs. They might be able to sense pheromones and send signals to the brain that are relayed to the complex hormonal system that regulates menstruation and, perhaps, other biologic processes involved in reproductive behavior.
The theories about human pheromones are intriguing, but do they actually stimulate attraction to a potential mate? That’s something fun to ponder as Valentine’s Day approaches, but we have no proof yet.
(Robert H. Shmerling, M.D., is associate professor of medicine at Harvard Medical School and clinical chief of rheumatology at Beth Israel Deaconess Medical Center in Boston. For additional consumer health information, please visit www.health.harvard.edu.)