Sniff test: How smell could be the hidden key to choosing friends

Last week I had one of those small, funny moments that sticks with you.

I was pushing Emilia’s stroller down our street in Itaim Bibi when a woman passed by wearing a clean, soapy scent that reminded me of my college roommate’s laundry powder.

I looked up without thinking and smiled. She smiled too. We kept walking, strangers again, but I noticed the way that little whiff nudged my body into friendliness before my brain even caught up.

I used to chalk things like that up to nostalgia. Now there is growing science that suggests smell might do far more than color a memory. It might quietly shape who we feel drawn to as friends. The idea sounds almost too simple, but the evidence is getting richer. And it is not just a single study making the claim.

What scientists are actually finding

In 2022, a team at the Weizmann Institute in Israel asked a very human question: when two people say they clicked right away, is there something chemical about that click.

They recruited pairs of nonromantic, same sex friends who reported that instant bond, collected the T-shirts those friends had slept in after a scent-control regimen, and then compared those shirts using both an electronic nose and human smellers.

On average, the friends’ body odor signatures were more similar to each other than to random pairs.

The team also ran a separate experiment with strangers. They used the electronic nose to predict which pairs would report better vibes in a short, silent interaction.

The prediction worked better than chance. That does not prove smell alone makes a friendship, but it points to a real signal living in the air between us.

This year, researchers led by psychologist Vivian Zayas added a fresh angle.

They ran a speed-friending study with young women who met for quick four minute chats. Before the meeting, each participant wore a plain cotton shirt to capture what the authors call a diplomatic odor, which reflects both natural scent and the everyday products we use.

Other participants judged the T-shirts by smell alone. Those scent based judgments tracked closely with their later judgments after the in person chats, and interestingly, a good conversation could nudge later scent ratings up.

That suggests our noses play a role, but our impressions can reshape how we interpret what we smell. It is a dance between perception and chemistry, which is very human.

If you saw a popular headline about this recently, it may have come from consumer friendly coverage that rounded up the findings in plain language.

The core claim, though, traces back to those two peer reviewed sources. One asks whether already close friends smell more alike than chance would suggest and whether smell can forecast a friendly click between strangers.

The other asks whether our individual scent preferences align with who we feel we could be friends with, and how a short interaction shifts that perception. When you put them together, you get a picture that is both intuitive and testable.

What this means in real life

I think about my own circle here in São Paulo. Half my girlfriends lean vegan or vegetarian, which means shared meals center around greens, beans, and spices. We exercise. We all have babies or plan to, so our routines are built around naps, quick showers, and simple skincare.

To a scientist, that lifestyle bundle is a cloud of volatile molecules. Laundry soap choice. Shampoo. Deodorant. The cumin we used last night. A hint of milk lotion on a baby’s shirt.

It is not hard to imagine that people who live similarly might smell a bit more alike, and that our noses map those similarities to a sense of ease.

There is a tempting shortcut here. If smell matters, should we try to smell like the people we want to befriend. I do not think that is the takeaway.

The Zayas team uses the term diplomatic odor for a reason. The way we clean and scent ourselves is part preference, part identity, part culture. It is a signal we choose.

So of course it influences who feels like “my people.” But the studies also point to something deeper that is less curated. The skin chemistry that comes from diet, microbiome, and biology interacts with those choices.

You end up with a personal signature that you do not fully control. A signature that your friends might just happen to share enough of.

The limits, and why they matter

A few important boundaries are worth naming. The Weizmann study looked at same sex, nonromantic dyads and focused on pairs who self described as click friends.

That is a special case. It is the fast bond you feel in the first hour, not the slow trust that grows over years of shared life. The sample sizes were also modest. Elegant lab work often is, because running controlled scent studies is hard.

Shirts must be prepped with unscented soaps. Diet gets controlled. Volunteers give up their deodorant for a few days. The upside is clean data. The downside is generalizability. The authors are careful about that point.

They suggest smell is a piece of the puzzle, not the whole picture.

The Cornell study also focused on young women and short interactions.

That is a specific social slice. We cannot assume that the same dynamics apply across ages, men, mixed gender groups, or across different cultural scent norms.

Still, the core finding that smell only judgments aligned with later face to face impressions, and that interaction quality could shift later smell ratings, is a real contribution. It tells us perception is active.

We do not just sniff and decide. We learn, and our noses update along with our minds.

How I am using this insight at home

I am a routines person. Our house runs on early breakfasts, shared stroller walks, tidy kitchen counters, and a quick four step skincare routine that fits between a baby bath and story time.

Reading this research nudged me to notice how much of friendship lives in the environment we create for one another. When my girlfriends come over for dinner, I open the windows, simmer garlic later so it does not dominate the room, and skip heavy candles.

We sit shoulder to shoulder while the babies crawl, and there is a light, clean smell in the air. It sounds almost cosmetic, but it sets a tone, and the conversation follows.

I also noticed how fast scent writes memory. After we spent a week in Santiago with family help, I unpacked at home and the suitcase held that soft, mixed smell of Yankee Candle and coffee.

It made me feel instantly cooperative. If a friendly scent can open me up to a better interaction, then maybe I can use that on purpose. Choose a signature detergent that feels like “us.”

Keep fewer competing scents in the house. Let the fresh food and clean laundry lead.

What this could change about how we meet people

I keep thinking about the practical settings where friendships begin. Co working spaces. Gyms. Toddler classes.

If scent shapes first impressions, maybe the best social design is simpler than we thought. Good ventilation. Fewer clashing air fresheners. A place to store coats and gym bags so the space does not carry a heavy mix. Little choices that make it easier for our noses to do their quiet sorting, without overwhelming the room.

For anyone who feels they struggle to click with new people, this research also offers a kind frame. It is not always that you said the wrong thing. Sometimes your bodies just did not hum together. That is not a moral judgment.

It is biology and personal preference playing out in a subtle way. As noted by the Weizmann team, there really can be “chemistry in social chemistry,” which is both literal and metaphorical. That helps me take things less personally when a connection does not land.

Two short quotes I keep in mind

“People who click with each other have similar body odor.” That simple line, from the Weizmann group’s summary of their Science Advances paper, captures the heart of their finding.

It does not say smell is destiny. It says smell is one of the early signals that can align with an instant bond, which feels true to lived experience. 

“Judgments based on the live interaction predicted changes in a second round of odor judgments.” That observation from the Cornell coverage highlights how flexible perception is. A good conversation can literally make someone smell better to you.

Bottom line for curious self observers

Your nose is part of your social brain. It might nudge you toward people who feel familiar, safe, and easy to be around.

It might also soften or sharpen after a good or awkward first chat.

The emerging science does not ask you to game this system. It invites you to respect it.

If you get a sense that you and someone else have a natural comfort, it may not be your imagination. If you do not, that is fine too.

Keep the room fresh, keep your routine true to you, and let the right people find their way to your table.

For readers who want a plain language overview, this explainer captures the landscape in one place and links the popular claim back to the research roots.