[summary]

A perfume that one person loves may be repulsive to another. The difference is in our genes, a new study suggests.

Scientists asked people to rate their preference for the scents commonly found in perfumes, and then tested for variations in the participants' genes. As it turns out, which version of a gene someone had was correlated with which smells they liked best.

"It's really hard for many people to find that perfect perfume for themselves," said August Hammerli, first author of the paper and a researcher at the Swiss Federal Institute of Technology in Zürich. “Many people judge in terms of packaging and marketing and not what smells they like. Our idea was to bring biology into this question and ask: Can we determine what perfume scents a person would like based on their genotype?”

The new study was published online Dec. 6 in the International Journal of Cosmetic Science.

What Smells Good?

Previous research has found that a set of genes called MHC genes (short for major histocompatibility complex) is related to whether someone is sexually attracted to someone else's scent. People are most likely to be attracted to the scent of someone who has different MHC genes than they do. Evolutionary biologists think that for primates in the wild, this helps ensure that animals closely related to each other don't mate.

Hämmerli and his colleagues hypothesized that our MHC genes may also dictate our preferences for other smells. One previous study suggested that there was a correlation, but didn’t flesh the idea out.  Hämmerli's team recruited 116 study participants — both male and female — and asked them to smell 10 different scents, including cedar, rose, cinnamon and moss. They repeated the tests with different concentrations of the scents and in different settings.

Some smells were clear winners and losers — the highest rated was tolu, a scent that comes from a South American balsam tree and resembles vanilla. The lowest rated was vetiver, which originates from a grass in India and is said to have a "woody" or "earthy" scent. But for each scent, the strength of the participants' preferences varied depending on each person's particular set of MHC genes .

"It would still be difficult to create a perfect perfume for someone based on this limited information," Hämmerli said. "But the more scents and people you study, the more patterns start to emerge."

Hämmerli said the scents that people prefer may be those that best advertise their own natural body odors to potential mates, enhancing the connection between MHC and attraction to others. But that theory has yet to be tested.

Buying Perfumes for Others

"These findings fit very well into what has been found,” said Claus Wedekind, of the University of Laussane in Switzerland. Wedekind was one of the first scientists to discover the link between MHC genes and mate preferences, with the notorious "sweaty T-shirt study" in which women rated their preference for the smells of T-shirts worn by different men.  

"We first tested this idea in the early 1990s in humans," Wedekind said. "We found that body odor preferences are indeed linked to immune genes. One could then speculate that other odor preferences are also influenced by these genes."

Because MHC genes are most often linked to people's attraction to others, biologist Leslie Knapp at the University of Cambridge said the new study could be expanded to test whether the perfume preferences hold true when the perfumes are worn by others, as opposed to sprayed on one's own body.

"In this study they're focusing on self as opposed to focusing on others," Knapp said. "When they talk about wanting to choose a fragrance, my idea is why aren't you thinking about what fragrances you'd be buying for your partner? If someone likes a fragrance, they should want their partner to smell like that."

But this line of research still has the potential to reveal how MHC genes control scent preferences, and why.  "A lot of people are interested in this because they still don’t understand it, and there's a lot more for us to learn," Knapp said. ”What is it that makes people prefer different smells, and what is it that makes different people smell different?"

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