Pheromones are chemical signals released by an organism that influence the behavior or physiology of others within the same species. Unlike the scents we consciously perceive, genuine pheromones are often odorless to the human nose, or detected below conscious awareness. The chemicals people commonly mistake for pheromones are actually components of body odor. True chemical signals act as silent messengers, triggering non-conscious responses rather than a recognizable scent.
The Scientific Paradox of Smell
The traditional sense of smell, the olfactory system, detects volatile compounds that travel through the air. However, pheromone detection in many mammals is managed by a separate structure called the vomeronasal organ (VNO), or accessory olfactory system. Located in the nasal septum, this organ detects non-volatile chemical signals, often requiring direct contact or high concentrations.
In adult humans, the VNO is considered vestigial, meaning it is a remnant structure that has lost its original sensory function. While a pit or duct corresponding to the VNO is found in most adults, the neural components necessary to transmit pheromonal signals to the brain are largely non-functional. If humans detect chemical signals, it is likely through the main olfactory system or other chemosensory pathways. This ability is a subtle, non-stereotyped function, rather than the instant, hardwired response seen in many other species.
Body Odor Versus Pheromones
The distinction between smellable body odor and an odorless chemical signal is based on the chemical nature of the compounds. Body odor is primarily composed of volatile organic compounds (VOCs) that easily evaporate and travel to the olfactory receptors. These VOCs result from skin bacteria breaking down initially odorless secretions from apocrine and sebaceous glands, especially in the armpit and groin areas.
Human chemical signaling molecules are often non-volatile steroids that do not readily become airborne. Although secreted alongside odorous compounds in sweat, the behavioral effects are attributed to the molecule itself, not the strong, often musky or urine-like smell perceived from the steroids.
Chemical Signals That Influence Behavior
The most studied human chemical signals are the steroid derivatives androstadienone and estratetraenol. Androstadienone is present in male sweat and semen, being a metabolite of testosterone. Exposure has been shown to affect the mood of women, sometimes improving it and heightening their focus when processing emotional information.
Estratetraenol is an estrogen derivative found in female urine and has been found to affect autonomic responses and mood in men. Studies have shown that when exposed to these compounds, recipients can be subtly biased in their gender perception of visual stimuli, suggesting a subconscious communication of gender-specific information. These effects are modulatory, meaning they influence the recipient’s internal state and perception rather than triggering an immediate, fixed behavior like a true releaser pheromone in insects.
Pheromones in Marketing and Pop Culture
The concept of a “pheromone smell” is fueled by the commercial market for “pheromone perfumes” and sprays. These products promise guaranteed attraction by including synthetic versions of compounds like androstadienone. The marketing often conflates the subtle, non-conscious effects observed in scientific studies with the idea of an irresistible, conscious scent.
The claimed efficacy of these commercial products in enhancing attraction is speculative and lacks definitive scientific support. Any perceived increase in success is often attributed to the placebo effect, where the wearer’s belief in the product boosts their confidence, leading to more positive social interactions. Therefore, the popular notion of a pheromone scent is more a reflection of marketing hype than a scientifically validated phenomenon.