Most pheromones have no detectable smell at all, at least not one you would consciously register. The handful of candidate human pheromone molecules that people can smell produce wildly inconsistent descriptions: the same steroid compound will strike one person as intensely sweaty and urine-like while the person beside them finds it pleasantly sweet or woody, and a third person smells absolutely nothing. That split is not a matter of opinion or nose sensitivity in the usual sense. It traces to genetic variation in a single olfactory receptor, making pheromone perception one of the starkest examples of how biology can make two people inhabit genuinely different sensory worlds.
The Steroid That Smells Like Everything and Nothing
The compound most thoroughly studied for its smell in humans is androstenone, a steroid found in human sweat and, more famously, in the saliva of male pigs, where it functions as a sex pheromone. When researchers ask people to sniff it under controlled conditions, the results are all over the map. Among those who can detect it, the most common descriptors are “harsh,” “sweaty,” and “sharp.” Some people use words like “sweet,” “floral,” or “woody.” On average, perceivers rate androstenone as unpleasant, and women tend to rate it as significantly more unpleasant than men do.1PubMed Central. Olfactory training in specific anosmia to androstenone and its association with genetic variations of OR7D4 In livestock science, the compound’s “intense urine-like odour” is the main culprit behind boar taint, the off-putting flavor in meat from uncastrated male pigs.2Livestock Production Science. Compounds responsible for boar taint, with special emphasis on androstenone: A review
Then there are the related steroids. Androstadienone, found in male sweat, is often described as musky or slightly woody at the concentrations where people can detect it. In lab settings it requires a surprisingly high concentration to reach conscious detection. Androstenol, another steroid derivative present in fresh sweat, is usually described as musk-like and tends to receive more neutral or even mildly pleasant ratings compared to androstenone. But here is the catch: none of these descriptions hold universally. What a steroid pheromone candidate “smells like” depends less on the molecule and more on the person doing the smelling.
Why the Same Molecule Smells Completely Different to You and Your Friend
Roughly 30 percent of people are specifically anosmic to androstenone, meaning they cannot smell it at any concentration. One older study put the figure even higher, at about 46 percent.3Chemical Senses. SPECIFIC ANOSMIAS TO 5α-ANDROST-16-EN-3-ONE AND ω-PENTADECALACTONE: THE URINOUS AND MUSKY PRIMARY ODORS The range across studies likely reflects different testing methods, but the consistent finding is that a huge fraction of the population is blind to this supposedly important chemical signal. Researchers classify the resulting gap as a “specific anosmia,” a condition in which a person with otherwise normal smell simply cannot detect one particular odor category. Androstenone anosmia corresponds to the “urinous” primary odor class, one of a handful of fundamental odor categories identified by researchers alongside “sweaty,” “musky,” “fishy,” “malty,” and “spermous.”4Chemical Senses. SPECIFIC ANOSMIA AND THE CONCEPT OF PRIMARY ODORS
The reason for this dramatic split has been traced to a specific olfactory receptor gene called OR7D4. This receptor is selectively activated by androstenone and the related steroid androstadienone. A common genetic variant of this receptor, involving two amino acid substitutions, severely impairs its function. People who carry two copies of the fully functional version tend to be more sensitive to both steroids and find their odors more unpleasant. Those carrying one or two copies of the impaired variant are less sensitive, rate the smell as less offensive, or cannot detect it at all.5Nature. Genetic variation in a human odorant receptor alters odour perception This finding has held up in applied settings: when researchers served cooked pork containing various levels of androstenone, people with two functional copies of OR7D4 tended to rate the meat as less appealing, while those carrying the impaired variant were more accepting of it.6PubMed Central. Genetic variation of an odorant receptor OR7D4 and sensory perception of cooked meat containing androstenone
So if you have ever been baffled when someone complained about a body odor you genuinely could not detect, OR7D4 variation is a plausible explanation. Your receptors may differ at this one locus enough to make the signal invisible to you.
Pheromones You Cannot Consciously Smell at All
The steroids that produce a detectable odor in some people are actually unusual among candidate pheromones. Most chemical signals thought to influence human behavior operate below conscious awareness. In one study, researchers exposed participants to androstadienone while they evaluated facial expressions. The participants did not rate the compound’s odor as different from control conditions in pleasantness or familiarity. They could not consciously tell they were smelling anything meaningful. Yet their judgments of the faces shifted: heterosexual men exposed to androstadienone perceived male faces as less angry, while heterosexual women perceived female faces as angrier.7PubMed. Sex-specific effects of human chemosignal on perception of angry but not fearful faces
This pattern of subliminal influence shows up repeatedly. When women were exposed to the chemical signature of fearful sweat from male donors, they became more likely to interpret ambiguous facial expressions as fearful, but only when the expression was genuinely ambiguous. Clear expressions were unaffected. The women did not report smelling fear or anything unusual.8PubMed. Fear-related chemosignals modulate recognition of fear in ambiguous facial expressions In a separate study testing emotion perception through odor cues, participants again rated the different odor conditions as indistinguishable in pleasantness and familiarity, confirming that the chemosignals were not consciously perceived as different from controls.9Translational Psychiatry. Emotion perception through the nose: how olfactory emotional cues modulate the perception of neutral facial expressions in affective disorders
This creates a strange paradox for the question in the title. A pheromone that genuinely influences your behavior might be one that, by definition, you cannot describe the smell of. You respond to it, but you do not experience it as having an odor. The molecules that we can consciously smell and describe, like androstenone, are simultaneously the ones whose status as true human pheromones remains most debated.
How Armpit Bacteria Create the Smell
One reason human body odor is so variable and complex is that the molecules secreted by your sweat glands are not the same ones your nose ultimately encounters. Apocrine glands in the armpit release steroids, including androstadienol and androstadienone, that are only weakly odorous or even odorless in their original form. Aerobic bacteria living on the armpit skin, particularly coryneform bacteria, convert these precursors into more pungent molecules. Androstadienol and androstadienone are transformed into compounds like androstenone and androstenol, which have much stronger odors and exceed the olfactory threshold that humans can detect.10The Journal of Steroid Biochemistry and Molecular Biology. Comparison of 16-Androstene steroid concentrations in sterile apocrine sweat and axillary secretions
This means the “smell” of a candidate human pheromone is partly a bacterial product. The same steroid precursor secreted by two people could produce different ratios of end products depending on each person’s skin microbiome. And the perceiver’s genetic makeup, as described above, further filters what that cocktail actually smells like to them. The signal goes through at least two layers of biological transformation before it registers as a conscious odor, if it does at all.
Fear Sweat and Other Emotional Chemosignals
Aside from the steroid pheromone candidates, researchers have been investigating a broader category of human chemical communication: emotional chemosignals carried in sweat. When people experience intense fear, they produce more armpit sweat, and that sweat releases more volatile molecules than sweat collected during calm states. In one study, higher fear intensity corresponded to greater sweat production and a higher dose of volatiles, suggesting a dose-response relationship where more intense emotion creates a stronger chemical signal.11PubMed Central. Encoding fear intensity in human sweat
An exploratory chemical analysis of fear sweat identified hexadecanoic acid (also known as palmitic acid) as one of the most abundant compounds present. When researchers isolated hexadecanoic acid and tested it separately, exposure to it reproduced some of the behavioral effects observed with the full fear sweat samples.12PubMed Central. Unraveling the universality of chemical fear communication: evidence from behavioral, genetic, and chemical analyses Hexadecanoic acid is a common fatty acid with no dramatically distinctive odor at low concentrations. If fear chemosignals have a “smell,” it is not the Hollywood version of danger having a sharp metallic tang. It is probably something bland enough that you would never consciously identify it as fear.
What Animal Pheromones Smell Like, for Comparison
In animals, the chemistry is often cleaner and the behavioral effects are far more dramatic. The textbook example is bombykol, the sex pheromone released by female silkworm moths to attract males. Bombykol is a volatile 16-carbon alcohol that works at extraordinarily low concentrations in air.13PubMed. Sexual attraction in the silkworm moth: structure of the pheromone-binding-protein-bombykol complex To a human nose, bombykol has no detectable smell. The male moth’s antenna is tuned with near-single-molecule sensitivity to this specific compound, but our olfactory system is simply not wired to pick it up.
Not all pheromones are volatile, either. Darcin, a sex pheromone in male mouse urine, is an involatile protein. It does not waft through the air at all. Instead, it works through direct contact, and it conditions other mice to prefer locations where the scent was deposited, even after the scent itself is gone.14PubMed. Pheromonal induction of spatial learning in mice If you stuck your nose in a dish of darcin, you would smell nothing meaningful, yet it drives powerful spatial learning in the animals that detect it.
The point is that “pheromone” does not imply “smelly.” In most animal systems, pheromones are detected through specialized receptor channels at concentrations far below the threshold that would register as a conscious odor even to the animal receiving the signal. The idea that a pheromone should smell like something specific is more a product of how perfume companies market their products than of how chemical communication actually works in biology.
The Vomeronasal Organ Question
Many animals detect pheromones through a dedicated sensory structure called the vomeronasal organ, separate from the main nose. Humans have a vomeronasal organ too, and it is present in the vast majority of adults. But anatomical and functional studies indicate it is probably vestigial, with no operational sensory role. It appears to lack the nerve connections and receptor types needed for active chemoreception.15PubMed Central. The clinical significance of the human vomeronasal organ
This does not mean humans cannot detect pheromones. It means that whatever chemical communication is happening likely goes through the main olfactory pathway rather than a specialized pheromone-sensing organ. Brain imaging studies support this: when men who had lost their sense of smell were exposed to estratetraenol, a steroid sometimes proposed as a female pheromone, they failed to activate the hypothalamic regions that lit up in men with normal smell. This suggests the signal was being routed through the standard olfactory system, not some hidden pheromone channel.16PubMed Central. Pheromone signal transduction in humans: what can be learned from olfactory loss Androstenol, meanwhile, activates the hypothalamus in women but through the conventional smell pathway, not a separate circuit.17PLOS ONE. Androstenol – a Steroid Derived Odor Activates the Hypothalamus in Women
Newborn Noses and Breast Secretions
One of the most convincing cases for functional chemical communication in humans involves the relationship between mothers and newborns. Secretions from the areolar glands, the small bumps surrounding the nipple, trigger strong behavioral responses in neonates. When exposed to these secretions, about 63 percent of newborns showed a clear increase in mouth and head movements, a response that was significantly stronger than any other stimulus tested, including breast milk itself and other body secretions.18PLOS ONE. The Secretion of Areolar (Montgomery’s) Glands from Lactating Women Elicits Selective, Unconditional Responses in Neonates These volatile compounds also stimulated eye opening and reduced crying.19PubMed. The “smellscape” of mother’s breast: effects of odor masking and selective unmasking on neonatal arousal, oral, and visual responses
What do areolar secretions smell like to an adult? Researchers have not characterized a single dominant odor compound. To a newborn, who has never smelled anything before, the question of “what does it smell like” may not even be the right framing. The response is innate and unconditional, more reflex than perception. This is arguably the closest thing humans have to a classic pheromone effect: an unlearned, species-wide behavioral response to a specific chemical stimulus. And the chemical responsible has no memorable smell to speak of.
What the Perfume Industry Calls a Pheromone
Walk through any duty-free shop and you will find fragrances marketed with the word “pheromone” on the label. The actual science behind these products is thin, but one compound has generated genuine research interest: methyl dihydrojasmonate, sold commercially as Hedione, a jasmine-scented molecule widely used in perfumery since the 1960s. Hedione smells pleasant and floral to everyone, which already sets it apart from the musky, sweaty steroids discussed earlier.
What makes Hedione scientifically interesting is that, compared to a standard floral scent, it produces significantly stronger activation in limbic brain areas including the amygdala and hippocampus, and it triggers a sex-differentiated response in a hypothalamic region associated with hormonal release.20PubMed. The smelling of Hedione results in sex-differentiated human brain activity Hedione also appears to bind to a type of receptor (VN1R1) originally associated with the vomeronasal system.21PubMed. Prior exposure to Hedione, a model of pheromone, does not affect female ratings of male facial attractiveness or likeability However, when researchers tested whether exposure to Hedione actually influenced how women rated men’s attractiveness, they found no effect. The brain lights up, but the behavioral needle does not move. It is a useful reminder that activating a pheromone-related brain pathway and functioning as a pheromone are two very different things.
How Exposure Changes What You Smell
Even for people who can initially detect androstenone, repeated exposure reshapes the experience. After sustained or repeated sniffing sessions, people’s detection thresholds shift, their perception of pleasantness changes, and the brain’s electrical response to the compound is altered. These exposure-driven changes do not occur equally for everyone: women show changes in later components of olfactory-evoked brain potentials that men do not, suggesting sex-specific neural plasticity in response to this steroid.22Neuropsychopharmacology. Repetitive Olfactory Exposure to the Biologically Significant Steroid Androstadienone Causes a Hedonic Shift and Gender Dimorphic Changes in Olfactory-Evoked Potentials
There is also cross-adaptation, in which adapting to one compound reduces your ability to smell a different compound. Androstenone and at least one structurally unrelated molecule with a perceptually similar character show mutual cross-adaptation, meaning that prolonged exposure to one dulls sensitivity to the other. The practical implication is that people who live or work in environments with chronic low-level exposure to these steroids, a locker room, a farm, a crowded household, may gradually lose the ability to detect what was once a pungent signal. Your nose essentially decides the signal is background noise and turns down the volume. The “smell” of a pheromone is not fixed even within a single person’s experience over time.