BBC - There is a wealth of psychological and biological information stored in our scent, but for some reason we choose to ignore it. Body odour can reveal details about our health, the presence of diseases (cholera smells sweet, acute diabetes like rotten apples), and our diet. Men find women's body odour more pleasant and attractive during the follicular phase of the menstrual cycle, when women are most fertile, and least pleasant and attractive during menstruation. 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. The gene complex that encodes for HLA 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. If you have a partner who is genetically dissimilar in immune profile, then your children will have a better resistance to pathogens. It is an advantage to have a child with someone who has a dissimilar HLA profile. If you have a partner who is genetically dissimilar in BO and immune profile, then your children will have a better resistance to pathogens. The mechanism that causes HLA-dissimilarity to result in a better-smelling BO is not known.
Do humans use genetic information hidden in body odour to choose their partners? It would seem not. In a study of 3,700 married couples, the likelihood of people ending up with a HLA-dissimilar partner was no different to chance. We might have a preference for certain smells, and there might be a genetic reason for that, but we don't act upon smells when choosing who we marry.
Couples who had high HLA-dissimilarity - which presumably happened by chance - had the highest levels of sexual satisfaction and the highest levels of desire to have children.
The link between BO preference and genes spurred a fashion for T-shirt speed-dating and even "mail odour" services. But the evidence to support the idea we can make good dating decisions based on smell is unclear. We might say we prefer something, but in practice it would appear we do not make choices based on that preference. Why not? It might be that real-life scenarios are too complex to use scent information accurately.
Mark Brooks: Dating based on odor? This is just too complex and unreliable to use as a component of compatibility in dating apps. But, perhaps that will change in the future.