Androstenone

The classic boar-taint pheromone and human sweat steroid; a single-receptor (OR7D4) model odorant whose perception is genetically variable rather than a systemic GABA-active neurosteroid.

Androstenone is an endogenous steroid encountered by humans mainly as a trace airborne odorant in sweat, saliva, and pork fat, and at these chemosensory exposures it has no established systemic toxicity. It is not used as an ingested drug or dietary supplement, and there is no recognized therapeutic dosing. As a purified chemical it is sold as a research reagent and as a fragrance or novelty "pheromone" additive; the principal reported effect in such contexts is the odor itself, which a substantial minority of people find strongly aversive.

Claims that topically applied androstenone reliably alters human attraction, mood, or social behavior are weakly supported and inconsistent across studies, so it should not be regarded as a proven behavior-modifying agent. In veterinary and food-science contexts, androstenone is the target of measures to control boar taint, including surgical or immunological castration, which reduces its accumulation in meat.

The 16-androstene steroids were first characterized in the mid-twentieth century as the malodorous principles responsible for boar taint, and androstenone was identified as a salivary pheromone of the domestic pig that triggers the mating stance (standing reflex) in estrous sows. Interest in a possible human role grew from the observation that androstenone is present in human axillary secretions and that its perception varies enormously between people, making it the textbook example of "specific anosmia," an inability to smell one particular compound despite otherwise normal olfaction.

Early population work suggested that roughly a third of adults were anosmic to androstenone, a figure later shown by rigorous forced-choice testing to be a methodological overestimate, with true anosmia nearer a few percent in young healthy adults. The field was transformed in 2007 when the odorant receptor OR7D4 was linked directly to androstenone perception and its genetic variants shown to predict individual sensitivity and hedonic response, providing the first demonstrated connection between a defined human odorant receptor and how an odor is consciously experienced.

Within sensory neuroscience and behavioral genetics, androstenone enjoys a strong reputation as a landmark model odorant; it is repeatedly used to dissect how a single receptor gene shapes conscious perception, to study specific anosmia, and to test whether olfactory sensitivity can be induced by repeated exposure. In animal science it is well known as a boar-taint marker and a genuine pig pheromone.

In the consumer and popular "human pheromone" market its reputation is far more dubious: it is marketed in colognes and attraction products on the strength of its endogenous presence and evocative odor, but controlled evidence that it functions as a human sex pheromone or reliably changes social behavior remains thin and contested. The scientific consensus treats androstenone as a genuinely neuroactive chemosensory steroid with an unusually well-mapped receptor genetics, while remaining skeptical of strong pheromonal claims in humans.