The science of smell,
and the technology built around it.
You have a better nose than they told you.
Most of us were taught that humans have a weak sense of smell. Dogs are the experts, our eyes do the real work, and smell comes in last. Almost none of that holds up, and the reason it became common wisdom is a little strange.
That famous 10,000 smells figure traces back to an offhand guess from the 1920s that everyone kept citing without checking. When a major U.S. university finally ran the experiment, they landed on something closer to a trillion distinguishable smells. Not a hundred times more. Closer to a hundred million times more. So your nose appears to be doing more varied work than your eyes and ears combined.
Drawn loosely to make the point. At true scale, the nose bar would run well off the page.
Smell is the only sense that reaches the emotional brain without a stop in between. Sight, sound, taste, and touch all pass through a relay first. Smell does not. It goes straight to the parts of the brain that handle emotion and memory, which is likely why a scent can move you before you have even named it.
If you are a woman, your nose likely does even more.
When researchers counted the cells in the olfactory bulb, the first place the brain registers a smell, women averaged about 43% more cells, and close to 50% more neurons, than men. Women also tend to score higher on tests of detecting and identifying odors. Worth remembering, since the people around you may catch a smell well before you do.
The thing you wear all day sits pressed against your skin, right under that sensitive nose. So it is worth talking about why clothes smell.
You have the nose. Here is what it spends all day smelling.
Sweat is innocent.
Here is the part most of us never learned. Sweat does not really smell on its own. Fresh sweat, straight off the skin, has almost no odor. It is mostly water, a little salt, and a few proteins and fats. Your body makes a lot of it, mostly to keep you cool.
So if sweat is innocent, what causes the smell? Bacteria. Specifically, the ones already living on you. Your skin is home to trillions of them, most harmless, many helpful. When sweat arrives, a few of them start breaking it down, and that is when the smell begins. Two come up more than the rest.
Lives in the warm, humid, folded areas of skin. Often behind the oniony smell that lingers even after deodorant.
The more active of the two. Usually behind the sharp, sour underarm smell most people would recognize right away.
There is one more piece, and it explains a lot. Not all sweat is the same. You have more than one kind of sweat gland, and they do very different jobs.
Millions of them, spread across almost the whole body. They make the thin, watery sweat that cools you down. It is mostly water and salt, close to odorless, and barely a meal for bacteria.
Fewer of these, clustered in the armpits and groin, and they switch on around puberty. Their sweat is richer, carrying proteins and fats. This is the one bacteria feast on, and where body odor really comes from. Its full purpose is still debated, and some of it may act as a faint chemical signal, but for smell it is the fuel.
A third type found mostly in the underarms, sitting somewhere between the other two. It can put out a lot of fluid, which tends to add to the load the bacteria have to work with.
Here is the catch. The apocrine taps open widest under stress, and stress sweat tends to be the strongest smelling of all. It is the one load that can outpace what a shirt alone is built to handle, which is a big part of why we made a deodorant to sit alongside it.
We tend to assume dogs and other animals have us beat on smell. Really, we just do not listen. We lean so hard on sight and hearing that most of what the nose reports never reaches our attention, while a dog builds its whole world from scent. The hardware is better than we give it credit for. We just tend to ignore it.
On your skin, a daily rinse keeps them in check.
Off your body, nothing keeps them in check.
Watch a fresh shirt turn.
A worn shirt keeps changing after you take it off. In the hamper, the bacteria that stayed in check on your skin suddenly have food, warmth, and nothing to stop them. Drag the slider to see what happens over the next few days.
This is not really the shirt's fault. Untreated fabric is just a warm, damp surface that bacteria are happy to grow on. Which raises the obvious question. If the problem is this old, surely we have worked out how to stop it. As it turns out, we have, and we have known for a very long time.
If time is the enemy, the right fabric should hold it off. So people ask about fabric.
It was never really about the fabric.
People often ask which material smells the least, as if the right fiber would solve the problem on its own. It helps to see what ordinary fabrics actually do about odor, which is not much. On their own, fibers do not fight bacteria. They differ only in how easy they make life for them. Here is how each one handles odor, and where each falls short.
It repels water but clings to the skin oils that bacteria turn into smell. Those oils sink deep into the fiber, so the odor often survives a wash and comes back within minutes of putting it on again. That is Permastink, and once it has set in it is nearly impossible to wash out.
The other common synthetic, all over gym gear and underwear. Like polyester it sheds water but holds the oils, and studies suggest it can absorb even more of the molecules behind odor, so the smell tends to linger just as stubbornly.
It soaks up sweat and holds it against itself. That leaves a warm, damp surface where odor-causing bacteria multiply until the fabric finally dries, so the smell tends to build as the day goes on.
It pulls in more moisture than cotton and spreads it out to dry faster, so sweat spends less time sitting on the fiber. Less damp time usually means less smell, which is why it tends to stay fresher than cotton.
Its smooth protein surface gives bacteria less to cling to than rougher cotton, which helps. But it also holds moisture and is slow to dry, so on odor it tends to land in the middle rather than ahead.
Pulls moisture off the skin and holds a limited amount of odor molecules in its core until the next wash, so the smell is slower to show than with most fabrics. If you get very sweaty or smelly, it does saturate.
Now notice what none of them do. Not one of these fibers actually fights the bacteria. Even merino only denies them the damp, and that runs out once the sweat keeps coming. If anything, the synthetics that took over wardrobes after the war made it worse, since our oiliest sweat clings to them hardest. So the fabric was never going to be the whole answer, which raises the obvious question of what is.
Basic fabric, alone, is not the answer, and that is why we use a three front strategy.
Prevent, slow, then absorb.
So HercLéon stopped shopping for the least hospitable fabric and built the defense into the fiber itself. We call it HercFiber, and it works in three stages, each leaning on materials chosen for that one job.
Pull sweat off the skin before bacteria can use it.
Disrupt any bacteria that still take hold.
Capture any odor that slips through.
And it is built in, not sprayed on.
Most anti odor fabric is sprayed with a finish that washes off within about twenty washes. HercFiber is woven in, so there is nothing on the surface to lose. It tends to hold about the same at wash fifty as on day one.
The fabric handles most of it. For the two things it cannot, we made a little help.
Where fabric needs a little help.
Fabric can do a lot, but not everything. Two problems sit outside what any fiber can reach, so we built a product for each.
Some smells are simply too strong for cloth. The body's stress signals, the ones tied to adrenaline, excitement, and anxiety, are among the compounds a human nose can catch at just a few parts per trillion. When the apocrine glands open under real stress, that can outrun what a shirt is built to handle. So we made a deodorant to stand alongside it.
Underwear runs into a different problem, one that is physical rather than bacterial, so no fiber can solve it. Nothing woven cleans up after a trip to the bathroom. Getting properly clean is the only real fix, which is why we made Buttler, our bidet, to handle what a waistband never could.
Put it together, and it comes out pretty simple.
So, that is the science.
Smell is bacteria, not you. Fabric can be built to make their job harder, and when it is, a shirt tends to stay fresh for days instead of hours. Fewer washes, less waste, and a lighter load to carry. That is the whole idea, woven in.
- Olfactory bulb neuron counts by sex: Oliveira-Pinto et al., PLOS ONE, 2014.
- Smell reaching the brain's emotion and memory centers without a thalamic relay: Cleveland Clinic; Harvard Medical School.
- The human olfactory receptor repertoire, roughly 400 functional receptors, and combinatorial coding: PNAS, 2019; Niimura et al.
- Detection of some odor compounds at a few parts per trillion: human odor-detectability research, Chemical Senses.
- Fresh sweat is odorless until skin bacteria act: Callewaert et al., Applied and Environmental Microbiology.
- Odor retention across fibers: McQueen and Abdul-Bari fiber studies; Woolmark and Lenzing material research.
- History of deodorant and antiperspirant: Smithsonian Magazine; Science History Institute.