Skipping showers is the latest trend. But is there any science to ‘pheromone’ maxxing?
Across parts of the internet where young men , the latest project is scent. Deodorant is out and washing less is in.
These “stinkfluencers” promise that the right aroma will work wonders on .
But while humans can find smells pleasant, or malodorous, or something in between, there’s no evidence we can detect and respond to pheromones, let alone produce one.
Many animals communicate with pheromones, often around . The problem is what happens when you look for the same sensory hardware in humans.
What is a pheromone?
A made inside the body of one member of a species, such as a cat, that’s secreted or excreted and reliably produces a response in another member of that same species.
It’s like openly broadcasting a chemical signal that is then by someone else.
Pheromones were first identified in silk moths back in 1959. That chemical, , is a sex-attractant released by female silkmoth to draw in mates.
A male silkmoth exposed to this pheromone will beat his wings and walk upwind toward the source. He doesn’t have a choice in the matter and his response is inbuilt, not learnt.
Other animals, . The purpose is usually to attract a mate or mark territory.
Not all animal pheromones have a fragrance
A pheromone isn’t defined by whether you can smell it or by which organ picks it up.
Some pheromones are volatile and smellable. Bombykol, for example, is detected by ordinary smell (olfactory) receptors on the moth’s antennae.
Others aren’t detectable to us at all, such as the people plug in to chill out their cats.
What makes a chemical a pheromone is the in members of the same species. Not whether it has a fragrance.
Humans don’t have the anatomy to receive the message
For a pheromone to be functional, something has to be able to receive it.
In many four-legged animals, that job falls to the , a small structure in the nasal cavity. It’s wired to a dedicated processing station in the brain called the .
But it doesn’t have to be a dedicated organ. Plenty of pheromones are picked up by the ordinary smelling infrastructure – the lining of the nose in mammals, or, in the case of the silk moth, receptors on the antennae.
Some humans have a . But from birth, there are , and no accessory olfactory bulb for a signal to report to.
What’s more, no chemical has ever been found in humans that meets the criteria to be labelled a pheromone.
Can’t sweat do something similar?
So if the signal isn’t there and we couldn’t receive it anyway, could the answer be in our sweat?
Not likely.
For a start, fresh sweat is practically odourless. Sweat is just a mix of 99% water, electrolytes (salts) and then tiny amounts of urea, ammonia and other compounds.
If you stay sweaty and avoid washing yourself, eventually that sweat will provide a cosy breeding ground for bacteria, and that will start to cause a stench. It’s unlikely to be an attractive odour.
But people can find smells attractive, of course. Though this is , such as fancying someone or being romantically involved with them.
What about the T-shirt study?
In a that gets a lot of play in the pop-psych and maxxing communities, male students wore a T-shirt for two consecutive nights after not washing with soap or using deodorants or other fragrant products.
Female students sniffed and rated six T-shirts each.
Both groups of students had also given samples for gene testing. Each woman was given three shirts worn by men whose major histocompatibility complex (MHC) genes (the ones her immune system uses to recognise invaders) were similar to her own, and three worn by men whose MHC genes were different.
The main result implied women preferred the smell of T-shirts worn by men with different MHC genes. But, among women taking the contraceptive pill, the preference switched. They rated men with similar genes as smelling better.
The interpretation was that women could sniff out men who are “immune-system compatible.” In other words, people with more variety in their MHC genes have more tools to fight off infection. So being attracted to mates whose MHC genes are different from yours means any resulting children will have stronger immune systems.
The idea didn’t come out of nowhere. Mate choice is influenced by scent in many other vertebrate species, and .
But the study doesn’t hold up well
Despite how T-shirt study caught the public imagination, there are two problems for pheromone maxxing.
First, the results don’t hold up all that well. A of all the studies that tested for MHC-odour effects in humans found no overall effect.
It also found evidence of publication bias. That happens when people get more exited about publishing their positive results, and when journals prefer the eye-catching stories.
We suggest that showering with soap and using deodorant is still the best route to maxxing olfaction-attraction. 
, Research Fellow in Public Health, and , Scientia Professor of Evolution,
This article is republished from under a Creative Commons license. Read the .
