https://www.usnews.com/news/health-news/articles/2022-06-24/smells-like-friendship-similar-body-odors-may-draw-folks-together

You and your best friend may have your noses to thank in helping bring you together, a new study suggests.

Researchers found that pairs of friends who'd just "clicked" upon meeting tended to smell more alike, compared to random pairs of strangers. What's
more, a high-tech electronic nose was able to predict, based on body odor, which strangers would hit it off during their first interaction.

The study was small, involving 20 pairs of "click" friends, but experts
said it
points to a simple fact: Sniffing is not only the realm of dogs, and
humans do
unconsciously use it in social interaction.

That's not to say people choose a lifelong bestie based on scent.

"But this does suggest there's a contribution of olfaction to forming friendship," said Valentina Parma, a researcher at Monell Chemical Senses Center in Philadelphia, who reviewed the findings.
...
Yet it's clear that olfaction is more important in human bonding than people generally recognize. Newborns are a prime example, Parma said. While their vision is not yet sharp, their sense of smell is. And they prefer the
scent of
their mother, and her breast milk, above all others.

There is also evidence, Parma said, that romantic attraction has a smell component -- and not just whether you like your date's choice of cologne.
...


https://www.science.org/doi/10.1126/sciadv.abn0154
There is chemistry in social chemistry

Abstract
Nonhuman terrestrial mammals sniff themselves and each other to decide
who is friend or foe. Humans also sniff themselves and each other, but the function of this is unknown. Because humans seek friends who are similar to themselves, we hypothesized that humans may smell themselves and others
to subconsciously estimate body odor similarity, which, in turn, may promote friendship. To test this, we recruited nonromantic same-sex friend dyads and harvested their body odor. We found that objective ratings obtained with an electronic nose, and subjective ratings obtained from independent human smellers converged to suggest that friends smell more similar to each other than random dyads. Last, we recruited complete strangers, smelled them with
an electronic nose, and engaged them in nonverbal same-sex dyadic
interactions. We observed that dyads who smelled more similar had more
positive dyadic interactions. In other words, we could predict social bonding with an electronic nose. We conclude that there is indeed chemistry in social chemistry.

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