Personal Olfactory Identification Information

 

Two things we will never fully understand, the human body, and olfaction, together.

Researchers explain the dissimilar smells of babies and teenagers

Mar 2024, phys.org

https://phys.org/news/2024-03-dissimilar-babies-teenagers.html

The researchers recruited the parents of 18 children aged up to 3 years old to wash the youngsters with a fragrance-free gel and to take swap samples of the armpits of their pajamas prior to sleep. They did the same with 18 teenagers between the ages of 14 and 18. All the cotton pads were then collected and analyzed in a lab setting.

The research team used mass spectrometry to identify the chemical compounds in the pads, and used gas chromatography along with a human sniffer to assess the odorousness of the smells associated with each chemical compound.

The researchers found that most of the chemicals responsible for body odor were similar between the two groups of volunteers. But there were a few that made the difference. Teenage sweat, for example, had high levels of many kinds of carboxylic acids, which the assessors described as "earthy, musty or cheesy."

They also found two steroids in the teen sweat not present in the baby sweat, one of which resulted in "musk or urine-like" emanations - the other, the assessors suggested, smelled more like "musk and sandalwood." Without such chemicals, the sweat of babies smelled much sweeter.

via a team of aroma chemists at Friedrich-Alexander-Universität Erlangen-Nürnberg with psychologists from Technical University of Dresden: Diana Owsienko et al, Body odor samples from infants and post-pubertal children differ in their volatile profiles, Communications Chemistry (2024). DOI: 10.1038/s42004-024-01131-4

https://dx.doi.org/10.1038/s42004-024-01131-4

Image credit: AI Art - Machu Picchu Face Girl - 2025

Clothes are like your second skin, so we can also call this body odor:

Textile scientists offer fresh insights on why some clothes get smellier

Jul 2024, phys.org

https://phys.org/news/2024-07-textile-scientists-fresh-insights-smellier.html

Cotton and viscose, which are cellulosic, or plant-derived fibers, absorbed - and consequently released - smaller amounts of odor-causing compounds than polyester, nylon and wool.

"Although we know that polyester is smellier after being worn next to sweaty armpits compared to cotton T-shirts, we haven't really known why."

"If you had a sweaty armpit that never actually touched the shirt you're wearing, then the fabric wouldn't get very smelly." The researchers soaked the fibers in the sweat solution for different periods of time, then examined the release of various odor-causing compounds.

Sweat is mostly made up of water but also has oily compounds that bacteria transform to form odors, and these oily compounds in watery sweat can interact differently with textiles, depending on the fiber chemistry.

"While water-loving cellulosic fibers such as cotton and viscose absorb more of the water from sweat than polyester does, polyester doesn't want to absorb the water. It's more oil-loving, and it absorbs more of the odorants, which don't dissolve in water, and more of the oily compounds.

The research also showed that although nylon and wool initially took in a lot of the odorants from the sweat, they dissipated them more quickly than polyester. After 24 hours, wool and nylon had much lower intensities of the odorants and were more similar to the cellulosic fibers.

"That tells us that while polyester still needs to be washed, for nylon and wool garments, people might be able to freshen them by just airing them out rather than laundering every time."

Bonus:

"The study's method of using simulated liquid sweat also offers an important fresh approach to exploring the issue."

via New University of Alberta and University of Otago in New Zealand: Rachel H McQueen et al, Textile sorption and release of odorous volatile organic compounds from a synthetic sweat solution, Textile Research Journal (2024). DOI: 10.1177/00405175241249462

https://dx.doi.org/10.1177/00405175241249462

Does fertility affect a woman's body odor? Study finds no evidence

Jul 2024, phys.org

https://phys.org/news/2024-07-fertility-affect-woman-body-odor.html

The researchers took samples of underarm odor from 29 women on 10 days spread over a menstrual cycle. A group of 91 men were then asked to rate the odor samples. In 16 of the women, the research team also looked at whether the chemical composition of the odor samples differed between the women's fertile and infertile days.

The results of both tests pointed in the same direction: there was no evidence from the odor ratings that men found a woman's odor more attractive on her fertile days than on her infertile days. 

Chemical analysis of the odor samples also showed no correlation between the composition of the underarm odor and the women's current fertility status.

via Leipzig University, the Max Planck Institute for Evolutionary Anthropology and the University of Göttingen: Madita Zetzsche et al, Combined perceptual and chemical analyses show no compelling evidence for ovulatory cycle shifts in women's axillary odour, Proceedings of the Royal Society B: Biological Sciences (2024). DOI: 10.1098/rspb.2023.2712

https://dx.doi.org/10.1098/rspb.2023.2712

On Handshakes and Animal Behavior

AKA Olfactory Sampling

Non-human primates Mark Zuckerberg and Pope Francis shaking hands and about to smell each other's chemosignals once they start covertly raising their hands near their face in about 20 seconds from now.

After you shake someone's hand, you smell your own hand. Sometimes the shaking hand, and sometimes the opposite, depending on the gender match. They call it "olfactory sampling," but we call it "smelling your fingers," and despite its being in poor taste while in public view, we do it almost neurotically, albeit covertly -- so covertly that even we don't notice ourselves doing it. 

I'm surprised this didn't resurface at the outset of the pandemic when we were all paying so much attention to how often we touch our face. In fact, the authors set us up thus:

Consistent with previous studies (Nicas and Best, 2008), we observed that humans often bring their hands to their noses. Of 153 subjects, 85 (55.55%) touched their nose with their hand at least once during baseline before the greet. Idle subjects had a hand (either right or left) at the vicinity of their nose for 22.14% of the time. (that's a lot of time!)

But this isn't just about how you can't keep your own hands off yourself:

Whereas facial self-touching has been considered a form of displacement stress response (Troisi, 2002), akin to rodent grooming, the novel framework we propose here for this behavior is that of olfactory sampling.

In this really carefully controlled study, they videotaped  hundreds of people after shaking hands with a greeter at the lab, and even outfitted the subjects tubes near their nose to monitor their sniffing behavior. The results were "unequivocal," and remind us that we are in fact animals, sniffing up a storm:

We found that humans often sniff their own hands*, and selectively increase this behavior after handshake. After handshakes within gender, subjects increased sniffing of their own right shaking hand by more than 100%. In contrast, after handshakes across gender, subjects increased sniffing of their own left non-shaking hand by more than 100%. Tainting participants with unnoticed odors significantly altered the effects, thus verifying their olfactory nature. Thus, handshaking may functionally serve active yet subliminal social chemosignaling, which likely plays a large role in ongoing human behavior.

*For example, by touching their nose when they were in the room on their own; ... Criterion for scoring was any application of a hand to the face, as long as touching was under the eyebrows and above the chin; n=271 down to 153.

And later on in the report, things get even more complicated:

The body odor of some of the experimenters was tainted by perfumes or gender-specific odors. Volunteers who shook hands with these tainted individuals behaved differently; when the experimenter was tainted with perfume the volunteers spent more time sniffing their own hands, but when the experimenter was tainted with a gender-specific odor they spent less time sniffing of their own hands. This shows that different smells influenced the hand sniffing behavior of the volunteers.

Now that you know, you might notice yourself doing it constantly. What would be really interesting now would be to somehow get some anosmics up in the mix, maybe congenitally, maybe some recent long covid anosmics, and see how these numbers change?

Notes:

Frumin I, et al. [incl Noam Sobel] A social chemosignaling function for human handshaking. eLife. 2015 Mar 03;4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4345842/