Whose odor is it, really?
Body odor is the work of our microbes.
What we secrete in sweat is, on its own, nearly odorless. The smell is made for us by the bacteria that live on the skin: certain staphylococci carry an enzyme that cleaves those silent precursors into the pungent thioalcohols we recognise. Body odor is not a failure of hygiene — it is biology, a collaboration between the body and its microbial life.
Tuned by genes, marked by time
Written into us, and changing with us.
- A single gene sets the volume. A common variant of ABCC11 leaves some people with little body odor at all — and, by the same switch, dry earwax.
- Age leaves its note. One particular compound, 2-nonenal, appears only after about forty and deepens with the years.
- How we live tilts it. Diet measurably changes how pleasant our scent is judged; and a newborn’s scent reaches straight into the reward centres of a mother’s brain.
It carries more than identity
Scent carries feeling — and sickness.
Sweat gathered while someone is afraid can pass that fear to a person who only smells it, often without knowing why — and disgust travels the same way. This channel runs below awareness, and it is processed differently in autism. Illness leaves a trace too: within hours of an immune challenge, a person’s body odor is judged less healthy and less pleasant. The body broadcasts a quiet, honest report of its state — though a non-specific one, a signal of sickness, not a diagnosis of which.
Unmistakably ours
A signature even perfume cannot overwrite.
Measured by chemistry, each of us carries a distinct, reproducible odor — an individual fingerprint. And perfume does not erase it: a fragrance blends with our own scent into a signature that is still, unmistakably, ours. We remain legible underneath. That is the quiet premise SHEMIM begins from — that a signal this personal, and this honest, is meant to be read, not buried.
How sure are we?
Every claim, tagged for how settled it is.
- Body odor is made by microbes, not the body alone: skin staphylococci use a dedicated enzyme to cut an odorless precursor into the pungent thioalcohols we recognise (Rudden et al., 2020; Minhas et al., 2015).
- A single gene sets how much we make: a common variant of ABCC11 leaves some people with little axillary odor — and dry earwax (Martin et al., 2010; Yoshiura et al., 2006).
- Our scent changes with age: the compound 2-nonenal appears only after about forty and rises thereafter (Haze et al., 2001).
- Each person carries a distinct, reproducible odor "fingerprint" measurable by chemistry (Penn et al., 2007).
- Scent carries feeling: sweat collected under fear or disgust evokes the matching response in people who only smell it — often without knowing (de Groot et al., 2012). These social chemosignals are processed differently in autism (Endevelt-Shapira et al., Nature Neuroscience, 2018).
- Scent carries sickness: hours after an immune challenge, a person’s body odor is rated less healthy and less pleasant (Olsson et al., 2014; Regenbogen et al., 2017).
- A newborn’s scent activates reward circuitry in the mother’s brain (Lundström et al., 2013); diet measurably shifts how pleasant our odor is judged (Havlíček & Lenochová, 2006).
- Perfume does not erase us: a fragrance blends with each person’s own scent into an individually distinct signature, rather than a uniform mask (Lenochová et al., 2012).
- The popular idea that we "smell out" genetically compatible mates (MHC/HLA) comes from real studies, but the largest analyses find the effect weak and inconsistent across populations (Winternitz et al., 2017). We hold it as an open question, not a fact.
Common questions
Frequently asked.
- What causes body odor?
- Body odor is produced by skin bacteria, not by the body alone. Staphylococci such as Staphylococcus hominis use a C–S lyase enzyme to cleave odorless precursors secreted in sweat into pungent thioalcohols (Rudden et al., 2020). A common variant of the ABCC11 gene determines how much precursor a person secretes — and also sets earwax type (Martin et al., 2010; Yoshiura et al., 2006).
- Can people smell illness or emotion in body odor?
- To a degree, yes. Hours after immune activation, a person’s body odor is rated less healthy and less pleasant (Olsson et al., 2014). Sweat produced under fear or disgust induces the matching state in people who merely smell it, often below awareness (de Groot et al., 2012). These are non-specific perceptual signals, not diagnoses.
- Does perfume hide a person’s natural scent?
- Less than assumed. A fragrance interacts with each person’s own body odor to form an individually distinct blend rather than a uniform mask, and people remain identifiable underneath (Lenochová et al., 2012). Each person also carries a reproducible chemical odor "fingerprint" (Penn et al., 2007).
Selected sources
- Rudden et al. (2020), Scientific Reports; Minhas et al. (2015), PeerJ — microbial production of body-odor thioalcohols.
- Martin et al. (2010), J. Investigative Dermatology; Yoshiura et al. (2006), Nature Genetics — ABCC11 and body odor.
- Haze et al. (2001), J. Investigative Dermatology — 2-nonenal and aging odor.
- Penn et al. (2007), J. Royal Society Interface — individual odor fingerprints.
- de Groot et al. (2012), Psychological Science — emotional chemosignals; Endevelt-Shapira et al. (2018), Nature Neuroscience — social chemosignals in autism.
- Olsson et al. (2014), Psychological Science; Regenbogen et al. (2017), PNAS — the scent of sickness.
- Lenochová et al. (2012), PLOS One — perfume and individual odor; Lundström et al. (2013), Frontiers in Psychology — infant odor and reward.
- Winternitz et al. (2017), Molecular Ecology — MHC and human mate choice (contested / largely null).
An honest signal, meant to be read.
If our scent is this personal and this truthful, the work is to read it — not to bury it. That is what SHEMIM studies, distinguishing evidence from inference at every step.