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When it comes to making careful plans to impress that significant other, certain things can seem like musts. Classy restaurant – check. Romantic atmosphere – check. Best suit or little black dress – check.

Many will pay just as much attention to how they smell, of course. And if it’s a special occasion, a gift of perfume might well be on the agenda too. Either way, read on. There are some must-knows about the science of smell and perfume that may well be new to you.

Image: Max Pixel

Smell is the dominant sense in many animals, including humans, and meetings between individuals usually begin with a period of intense mutual sniffing. From this olfactory exploration, animals glean relevant information about a potential mate’s fertility and quality, enabling decisions about whether to breed now or wait until someone better comes along.

Research on the perception of human body odour reveals that similar messages lurk within our armpits. Researchers commonly test such perceptions using armpit odour collected on worn t-shirts or underarm pads, the wearers having been asked to avoid using fragranced products beforehand.

In experimental tests, men find women’s odour more pleasant and sexy when they are in the fertile part of their menstrual cycle than at other times. Women are more attracted to odours of men who have attractive non-olfactory qualities, such as being socially dominant, facially attractive, or having an air of confidence about them. 

Our body’s natural smells also appear to provide a for couples to check out their genetic compatibility. Research using the same t-shirt method indicates that both sexes prefer the odour of potential partners who are genetically dissimilar when it comes to a set of genes known as the major histocompatibility complex (MHC). 

Research is now challenging the conventional view that perfumes simply mask bad odour. In one study, researchers asked participants to wear cotton underarm pads, as described above, but they were instructed to apply a particular fragrance under one armpit while leaving the other fragrance-free. Unsurprisingly perhaps, volunteer sniffers later found the fragranced armpit odour to be more pleasant.

But then the researchers asked a new set of participants to apply their fragrance of choice under one armpit and to apply another fragrance, chosen by the experimenters, under the other. This time, the sniffers judged the fragrance/body odour blends as more attractive when they involved the wearer’s own preferred fragrance – even though the sniffers found the two fragrances roughly comparable when there was no body odour involved. 

The conclusion? People select fragrances that complement their own body odour, producing a favourable blend.

A key study determined the MHC group of different sniffers and then noted which odours they preferred among a range of common ingredients that might contribute to a perfume that they would wear.

The results revealed a correlation between certain MHC groups and preferences for certain ingredients, suggesting that we choose fragrances that enhance the MHC signals that we are already giving off. Yet these correlations disappeared when the same sniffers rated the ingredients for a perfume their partner might choose to wear. At the genetic level, perfume preferences only work when thinking about ourselves.

Taken together, these studies suggest that we evaluate perfumes, at least in part, according to whether they suit our individual, genetically influenced odour.

So what lessons can be learned from these studies? One main point is that choosing a perfume for your partner based on your own preference is unlikely to work well. Your best bet is to ask perfume shop staff to select a perfume that smells roughly similar to the one you know your partner likes. Or do it yourself using perfume finders online, such as FR.eD or Nose.

For those choosing a fragrance for themselves, the lesson is to ensure you select one that really suits you. In the study of odour/fragrance blends, there were a few wearers who bucked the trend and smelled better with the experimenter-assigned perfume than with the brand they chose themselves.

So it’s always worth investing some time in making a choice, and to test-drive it on your skin first. 

- The Coversation

The Conversation