The Great Pheromone Debate
The question of whether humans possess pheromones has sparked scientific controversy for over 50 years. While the pheromone industry generates millions in sales annually, the scientific community remains divided on a fundamental question: do true human pheromones actually exist?
The answer depends heavily on how you define “pheromone” and what level of evidence you require. This article examines what the science actually shows.
Defining the Terms
What is a Pheromone?
The term “pheromone” was coined in 1959 by Karlson and Luscher to describe chemicals that:
- Are produced by one member of a species
- Trigger a specific, stereotyped behavioral response in another member
- Work reliably across all members of the species
- Operate through dedicated sensory pathways
By this strict definition, classic examples include:
- Bombykol: A single molecule that causes male silk moths to fly toward females
- Queen substance: Pheromone blend that controls bee colony behavior
- Mouse urine proteins: Trigger aggression or lordosis behaviors
What is a Chemosignal?
The term “chemosignal” is broader and includes any chemical that:
- Conveys information between individuals
- May influence behavior, physiology, or mood
- Can work through standard olfactory pathways
- May vary in effect based on context and individual differences
Most scientists now prefer this term for human chemical communication.
What the Evidence Actually Shows
Proven: Humans Produce Odorous Steroids
Multiple studies confirm that humans produce and secrete specific steroid compounds in sweat, particularly from the axillary (armpit) region:
- Androstenone (5alpha-androst-16-en-3-one): Found primarily in male sweat
- Androstenol (5alpha-androst-16-en-3-ol): Present in both sexes
- Androstadienone (4,16-androstadien-3-one): Higher in male sweat
- Estratetraenol: Proposed female compound, found in urine
These compounds are structurally similar to those used as pheromones in pigs, where androstenone triggers the mating stance in sows.
Proven: These Compounds Affect Human Physiology
The strongest evidence for human chemical communication comes from studies showing measurable physiological changes:
Cortisol Modulation (Wyart et al., 2007)
In a landmark study published in the Journal of Neuroscience, Wyart and colleagues found that women who smelled androstadienone maintained significantly higher cortisol levels compared to controls. This effect:
- Occurred with just 20 sniffs (no skin contact needed)
- Was statistically robust
- Suggests hormonal communication via smell
Brain Activation (Savic et al., 2001, 2005)
Using PET imaging, Ivanka Savic’s group at the Karolinska Institute found that:
- Androstadienone activates the hypothalamus in heterosexual women
- Estratetraenol activates the hypothalamus in heterosexual men
- Homosexual individuals showed response patterns matching their sexual preference
- These responses bypass typical olfactory cortex pathways
Mood and Attention Effects (Bensafi et al., 2004)
Multiple studies show androstadienone exposure:
- Elevates positive mood in women
- Increases attention to emotional stimuli
- Modulates autonomic nervous system activity
- Effects are dose-dependent
Uncertain: Whether These Meet “Pheromone” Criteria
Here’s where the controversy lies. For a compound to qualify as a true pheromone:
Problem 1: Effects Aren’t Universal
- Only ~50% of people can consciously smell androstenone
- Genetic variation in the OR7D4 receptor determines perception
- Effects vary based on context, menstrual cycle, and social setting
Problem 2: No Stereotyped Behavior
Unlike moth pheromones that reliably trigger specific behaviors, human responses to chemosignals are:
- Subtle rather than dramatic
- Context-dependent
- Modulated by cognition and social factors
Problem 3: Methodological Issues
A critical 2015 review by Doty argued that much pheromone research suffers from:
- Small sample sizes
- Failure to replicate
- Publication bias toward positive findings
- Contamination of “pure” compounds
Problem 4: The Replication Crisis
According to a 2020 analysis in Philosophical Transactions of the Royal Society B, researchers estimate that 30-40% of studies in this field may not replicate, mirroring problems seen across psychology.
The Vomeronasal Organ Question
In many mammals, pheromones are detected by the vomeronasal organ (VNO), a specialized structure in the nose that connects directly to the hypothalamus.
Humans have vestigial VNO structures, but:
- No neural connections to the brain have been confirmed in adults
- VNO genes are largely pseudogenized (non-functional) in humans
- Any pheromone effects likely occur through the main olfactory system
This doesn’t disprove human pheromones, but it does mean the detection mechanism differs from other mammals.
What IS Proven vs. What IS NOT
What the Science Supports
- Humans produce odorous steroids with structural similarity to animal pheromones
- These compounds affect physiology including cortisol, mood, and brain activation
- Body odor carries information about genetics, health, and emotional state
- Olfaction influences mate preferences particularly regarding MHC/immune compatibility
- Fear and stress can be chemically communicated between individuals
What Remains Unproven
- Any single compound that triggers reliable, universal behavioral responses
- That androstadienone or androstenone are true pheromones by strict definition
- That commercial “pheromone products” produce the effects they claim
- The existence of a functional human vomeronasal system
The Terminology Solution
Most researchers now use the term “chemosignal” rather than “pheromone” for human compounds. This acknowledges that:
- Chemical communication occurs in humans
- Effects are real but context-dependent
- The mechanism differs from classic pheromone systems
- Strict pheromone criteria may not apply to humans
As Wysocki and Preti noted: “The term ‘putative pheromone’ is used because in humans, there is no substance that has been demonstrated to fulfill all the criteria required for a pheromone.”
Why This Matters for Pheromone Users
Understanding the science helps set realistic expectations:
What You Can Reasonably Expect
- Subtle shifts in mood or social perception
- Context-dependent effects that require the right setting
- Individual variation in both projection and reception
- Effects that work alongside (not instead of) normal social cues
What You Should Be Skeptical Of
- Claims of dramatic, guaranteed effects
- “Instant attraction” promises
- Products claiming to contain “human pheromones” without specifying compounds
- Universal effects that work on everyone
The Bottom Line
Do human pheromones exist? The honest scientific answer is: probably not in the classical sense, but humans clearly engage in chemical communication.
The evidence supports that:
- Specific steroids in human sweat affect the physiology and mood of others
- These effects are real but subtle and context-dependent
- Calling them “pheromones” may be technically incorrect
- Calling them “chemosignals” is more accurate
For the pheromone community, this means the molecules being used likely do have effects, but those effects are nuanced and work within the broader context of social interaction rather than overriding it.
Key Takeaways
- Strict definition: No compound meets all criteria for a true human pheromone
- Broader view: Humans clearly communicate chemically, but effects are contextual
- Androstadienone: Best-studied compound; affects cortisol, mood, and brain activity
- OR7D4 genetics: Explains why people perceive these compounds differently
- Practical impact: Expect subtle, supportive effects rather than dramatic ones
- Terminology: “Chemosignal” is more accurate than “pheromone” for humans
Scientific Confidence
Confidence Level: Medium
The existence of human chemical communication is well-supported. Whether any compound qualifies as a “true pheromone” by strict definition is doubtful. The effects of compounds like androstadienone are reproducible but subtle and context-dependent. Commercial pheromone product claims often exceed what science supports.