The Nose Knows


Ever wonder why you're so drawn in by some people's scents and turned off by others?

According to Wikipedia: “A a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual.” In a previous post we discussed how hormones, specifically the hormone oxytocin, have a large impact on our emotions and responses in romantic relationships. In this post we will discuss how another factor that influences us is our ability to detect a subtle, odorless chemical emanating from our potential love interest that causes us to respond on a visceral, animalistic level. That olfactory trigger is known as a sex pheromone. Despite the sophistication of our modern world, we are largely primal creatures driven by our biology, and it’s important to have a handle on this information in order to have every possible advantage in the rough terrain of modern dating. If you’ve ever been driven wild by the scent of a man you were interested in and didn’t know why, read on.

You may recall hearing about the famous white tee-shirt study conducted by Claud Wedekind where “Forty-four men wore the same T-shirt for three days. They refrained from deodorants and scented soaps so they wouldn’t interfere with their natural smell. Women then sniffed the shirts and indicated which ones smelled the best to them. By comparing the DNA of the women and men, the researchers found that women didn’t just choose their favorite scent randomly. They preferred the scent of man whose major histocompatibility complex (MHC)—a series of genes involved in our immune system—was most different from their own. Researchers knew to look at the MHC because of its importance in animal’s sexual preferences. In mice, it has long been known that MHC not only helps ward off infection, but it also plays a role in scent and mate selection. From an evolutionary perspective, choosing a mate with a different immune system makes survival sense. Kids of parents with different immune genes are more likely to be disease-resistant and are therefore more likely to survive. The women in this study also reported liking the scents that reminded them of their current or previous boyfriends, showing that MHC attraction is consistent. And because MHC profiles differ greatly from one person to the next, there is no universally “good” smell. One woman’s Romeo was another woman’s raunchy.”

There is still a lot of debate in the scientific community as to whether humans can detect pheromones or not and if we can, exactly how much influence they have over our behavior, but according to some scientific research, when women are ovulating, we generate pheromones called copulins, which when a man smells them causes his testosterone level to rise. In reaction to this, the man produces androstenone, a pheromone which women who are not ovulating find undesirable. The Discovery Channel offers excerpts from its documentary on this subject titled “The Science of Sex Appeal” ( that is required viewing for a deeper understanding of this fascinating area of human attraction.

Of course if you are on the pill, this switches up the dynamic considerably, “An interesting exception to the MHC attraction is for women taking the pill. Wedekind found that pill-takers responded in almost the exact opposite manner than would be expected. Because the pill tricks your body into thinking it is pregnant, it chemically alters your sense of attraction. Instead of finding the scent of genetically dissimilar men attractive, women on the pill found the scent of men with MHC’s similar to their own to be attractive.” ( But according to Discover Magazine, “While mounting evidence suggests that having one’s hormonal levels smoothed out in this way alters some of the laws of attraction between men and women, scientists hasten to add that hormones aren’t everything.” In other words, despite the fact that we are greatly influenced by our biological urges, we still have a reasoning mind that makes decisions and ultimately decides whom we choose.

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This article was originally published at . Reprinted with permission from the author.