The idea that humans might communicate through chemical signals called pheromones has captivated scientists and the public for decades, inspiring countless studies in search of proof.
In animals, pheromones are well understood. Ants follow chemical trails to navigate and communicate, dogs mark their territory with scent signals, and moths release airborne pheromones to attract mates.
But whether humans do the same is a trickier question. Could someone really trigger a physical or emotional reaction in another person without them even realising? Could it tip the scales of attraction?
After more than 60 years of searching, the answer remains elusive – though new findings suggest we may finally be closing in on it.
First whiffs
In 1959, Adolf Butenandt and his team discovered the first pheromone, bombykol, a chemical released by female silkworm moths to attract males.
Soon after, scientists coined the term ‘pheromone’ to describe a chemical signal released by one individual that triggers a specific response in another member of the same species.
The floodgates were then opened to hunt for human equivalents.
One of the first high-profile human pheromone claims came in 1971, when Martha McClintock published a study reporting that the menstrual cycles of 135 women in a university dormitory appeared to synchronise over the year.
The phenomenon became known as the ‘McClintock effect’ and was widely claimed as evidence of a human pheromone. The finding crumbled under scrutiny, however, as other studies failed to replicate it and scientists showed that apparent synchrony can arise by chance.
Over the years, scientists have primarily focused on four main chemicals as possible human pheromones. Androstenone and androstenol have been linked to social perception and sexual attraction.
Androstadienone has been studied for its possible effects on women’s mood and attention, while oestratetraenol is thought to influence how men perceive women.
Yet none of these compounds have been conclusively proven to be a true human pheromone.
Studies often test them in doses far higher than the body naturally produces, making results unreliable, and many experiments are riddled with design flaws and weak statistics, leading to inconsistent and inconclusive findings.
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The T-shirt test
If you ever get into a discussion about human pheromones, Prof Claus Wedekind’s ‘sweaty T-shirt study’ from 1995 will probably be mentioned.
In this experiment, women were asked to smell T-shirts worn by men and rate which of them they preferred.
Interestingly, women not taking the contraceptive pill tended to favour the scent of men whose immune system genes (known as MHC genes) were most different from their own.
Evolutionarily, this makes sense, as choosing a mate with different immune genes can give children broader protection against disease.
The study has been replicated and is often cited as a strong example of human chemosignalling, a process in which body odours transmit social or biological information.
The trouble is, the scent involved in the study doesn’t meet the strict definition of a pheromone.
For starters, instead of being one chemical, a person’s complex personal ‘odour print’ contains several. And while pheromones can spark automatic, unconscious changes – like hormonal shifts or instinctive behaviours – this kind of scent works differently.
It shapes personal preferences, meaning the response is subjective and conscious rather than a reflex you can’t control.
Invisible clues
Although the famous T-shirt study may not have nailed the case for human pheromones, some scientists think the search is far from over.
Among them is Dr Tristram Wyatt, a Senior Research Fellow at the University of Oxford’s Department of Zoology, who has spent his career exploring how pheromones evolved.
“If you look at humans as just another animal, it would be surprising if we didn’t have pheromones,” he says. “For example, our body odours change at puberty and we get smellier, exactly at the time we reach sexual maturity.
"In other animals, those kinds of smells often carry important signals, so it’s very likely that humans have them too. We just haven’t proved it yet.”
Despite this likelihood, reliably confirming a human pheromone has proven extraordinarily difficult.
“Studying human pheromones is like looking for a needle in a haystack,” Wyatt says. “Humans emit thousands of smelly molecules, so it’s difficult to pinpoint which one is causing the effect.
“On top of that, our reactions to odours are shaped by culture, mood and individual differences, which makes behaviour highly inconsistent. Without a reliable bioassay – a clear, measurable response to a smell – it’s almost impossible to identify a true pheromone.”
Then there are the reproducibility problems. Many pheromone studies have been based on tiny sample sizes, making their results statistically shaky and prone to false positives.
Early experiments often lacked rigorous controls and the field suffers from publication bias – with positive results far more likely to make it into journals.
The result? An evidence base that looks stronger than it really is: a patchwork of intriguing but unreliable findings, with only a handful that hold up when tested again.
Hot on the scent
Despite decades of frustration, Wyatt remains optimistic and is particularly encouraged by a French study that may be the closest step yet towards identifying a human pheromone.
The research focused on secretions of lactating mothers from the areolar (Montgomery’s) glands – the small glands around the nipple that release tiny droplets during breastfeeding.
When researchers presented the scent of these secretions to newborn babies, they found that infants would instinctively turn their heads and start exhibiting suckling behaviours and searching for the nipple.
“This is the most exciting lead we have so far,” Wyatt says. “Any baby will respond to these secretions, even if they come from another mother.
"That kind of universal, instinctive reaction is exactly what we look for in a true pheromone. If we can identify the exact compounds responsible, it could finally give us the first proven human pheromone.”
Another recent breakthrough in pheromone research came in 2023, when scientists at the Weizmann Institute of Science, in Israel, studied the effect of tears cried by women.
When men smelled the tears of women who had watched a sad film, their testosterone levels fell, and brain scans showed changes in areas linked to both aggression and smell.
Researchers even identified four receptors in the nose that detected the chemical signal in the tears.
Researchers are now working on identifying the specific molecules in tears that cause this effect, which could potentially be manufactured to help calm aggression.
Yet while there is evidence that humans use smell in social and sexual contexts, we have yet to prove that we communicate through pheromones.
“If we want to finally prove whether human pheromones exist, we need to study them properly,” Wyatt says.
“That means clear tests that show consistent responses, larger and better-designed studies, and moving beyond the same old unproven molecules. Only careful, evidence-based research will give us real answers.
“The search for a true human pheromone has only just begun,” he says. “But with the right methods to guide us, we may finally be on the path to discovering it.”
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