Our body odor can reveal details about our health, as the presence of diseases (cholera smells sweet and acute diabetes like rotten apples). "It can also reveal information about our diet," says Mehmet Mahmut, an olfaction and odor psychologist at Macquarie University, Australia. "There are a couple of studies that kind of contradict, but my group found that the more meat you consume the more pleasant your BO smells."

While it can change depending on our diet and health, a lot of what makes our smell unique is determined by our genetics. Our body odor is specific enough, and our sense of smell accurate enough, that people can pair the sweaty T-shirts of identical twins with a group of strangers' T-shirts. Identical twin body odor is so similar that matches in this experiment even mistook duplicate T-shirts from the same individual as two twin T-shirts.

In one study, women were given T-shirts worn by random men and asked to rank them by how pleasant they were. Their order of preference followed the same pattern as something called Human Leukocyte Antigen (HLA) dissimilarity.

HLA is a group of proteins that helps our immune system to identify cells that belong to us and cells that are from something or someone else – and are therefore potential pathogens. The gene complex that encodes for HLA, called MHC, also encodes for some other proteins used in our immune response and is useful as a shortcut for scientists to see what kind of protections our immune system can offer.

 

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