It is Valentine’s Day and I want to talk to you about how you smell. This will not be a discussion about how your musky, earthy scent attracts a mate. No, we need to have a conversation about how your urinous, acidic odor might drive one away.

There are ways to safeguard against the Valentine's Day faux pas of smelly underarms. Think about what you will wear to celebrate the holiday. I’m going to make this simple – avoid polyester.

It seems like it would be easy to adhere to such advice, but consider possible Valentine’s Day agendas: a bike ride for two, a hike to a secluded picnic spot, a candle-lit prix frixe dinner. Athletic wear is an olfactory nightmare, but even a romantic, flowy blouse could ruin a date. Sporty or dressy, garments made from synthetic fibers smell worse than anything else in the closet. The reason why can be understood by examining the fibers’ chemical and physical properties.

Rachel McQueen is an assistant professor at the University of Alberta. Her research primarily focuses on the development and retention of odor in textiles. Because human odor profiles and fabric fiber structures are so complex, it is difficult to pick apart all the factors that lead to a garment retaining odor.

So Dr. McQueen started with the basics, answering the question: Does polyester actually have greater odor intensity compared to natural fibers? “A lot of people would probably think, ‘So what, I knew that, because when I go to the gym my polyester T-shirt stinks to high heaven,’” says Dr. McQueen. But she wanted scientific proof to validate these anecdotal stories. And she wanted to determine whether more odor intensity was associated with more garment bacteria.

While working on her doctorate at the University of Otago in New Zealand, Dr. McQueen and her colleagues performed a statistical analysis of bacterial population found on odorous garments. What they discovered flies in the face of what is commonly believed to be associated with textile odor.

I was in a stinky situation myself two weeks ago while attending ScienceOnline2013. This is no ordinary conference. Highlights of the Wednesday evening opening, at the North Carolina Museum of Natural Sciences, included finding out what kind of microorganisms live on your face and under your arms. While passing time, waiting to get sampled, I made small talk with fellow attendees, strangers, informing them that I do not wear deodorant. This topic of conversation made perfect sense in the context of the experiment for which we were all anxious volunteers. Later, I regretted the decision.

I don’t have a meaningful, philosophical explanation for why I don’t wear deodorant. One day I just stopped. That was five years ago and after a week without it I realized I didn’t always need it, so now I rarely use it.

It turns out some individuals are blessed with odor-free armpits. A research group in Hamburg, Germany identified a gene critical for odor formation. A single mutation in the gene, ABCC11, leads to complete odor loss in the carrier. Human body odor forms when bacteria consumes protein rich fluids secreted from glands in the armpits (among other places) leaving behind vile fatty acids, vinegar’s big brothers. The gene mutation means these odor molecules never become part of the secretion in the first place.

Unfortunately, few people with this mutation realize they are carriers. A study last month conducted in the UK found that 78% of people who carry the mutated gene still wear deodorant.

This is not surprising, considering that for 100 years we have been trained to wear deodorant. Like Pavlovian dogs, our societal response to puberty’s signals is doling out antiperspirant. Sarah Everts uncovered the history of antiperspirant in this story for Smithsonian magazine which explores how deodorant and antiperspirant became social norms.

All of this pit lit gives credence to my anti-antiperspirant stance, but unfortunately I don’t posses the ABCC11 mutation. The gene mutation also affects ear wax; you may be a carrier if yours is dry. Mine is quite sticky; besides, sometimes I smell. Just as I did the third morning of ScienceOnline2013 when I realized, mid fist pump, while screaming, “I’m a African” during the nine o’clock convergence (I told you this was no ordinary conference), that I had B.O. This is a disconcerting notion when you are surrounded by people you barely know, many of whom you have informed that deodorant application is not in your hygiene regimen. So when your associates catch a whiff of acidic odor, like Fifi the kitty in a Pepe Le Pew cartoon, there will be no doubt as to its origin.

I was too far from the hotel to return and change. So I kept my elbows pinned to my sides and convinced myself that the shirt would air out as I moved. At the end of the day I put the shirt to my nose; it was offensive. Then I dug my travel shirt out from the bottom of my suitcase. It smelled fine, like my laundry detergent. One shirt (made of cotton) had endured 18 hours of wear, including travel: on a train, on a plane, in a warm taxi, in a van full of people, through a lemur center (Oh my god, you want to talk about stench!) and by foot, several blocks. The other shirt (made of polyester) was foul within an hour. There had to be a scientific explanation.

When Dr. McQueen and her colleagues studied microbial populations on garments composed of different materials the findings were surprising. “Bacteria survives a lot longer on wool then on polyester and cotton,” says Dr. McQueen. Which is contrary to what was expected and – regardless of her findings – what we are still led to believe.

If odor molecules are the leftovers when bacteria eats, then it is presumed that a garment with less bacteria will have less odor. Because of this line of thinking, antimicrobial coatings are being researched and produced for athletic and healthcare attire. Dr. McQueen laments that even Merino wool manufactures will tout the fabric’s antimicrobial properties on their websites. Dr. McQueen laughs, “It's like, hang on, there's bacteria all over your body, there's bacteria all over a sheep's bodies. It doesn't make sense.”

The difference in surface morphology between the two fiber types is what is more likely to be responsible. Surface morphology describes the terrain of a fiber. A natural fiber like cotton or wool is highly textured compared to a manmade fiber which has a smooth surface. On a larger scale, these surface properties result in polyester having a sheen and wool being matte.

Dr. McQueen likes to picture wool as activated carbon. “The complexity of wool and its structure has a lot of different potential chemical binding sites,” she says. Not only is it possible for odor molecules to bind fairly strongly to the wool fibers, but the intricacy of natural fibers physically limit the ability of odor molecules to escape the fabric. If odor molecules don’t escape, then we can’t smell them. Odor molecules do not penetrate a polyester fiber and since there is only a weak surface interaction the odor molecules are free to travel into an olfactory system and register as unpleasant.

Microscope image of a wool fiber at 400x zoom.

Microscope image of a polyester fiber at 400x zoom. The dark dots on the polyester are delusterant within the fiber, not on the surface.

Rachel McQueen has further experiments to conduct to prove her hypothesis. She admits, “This is a really under studied area: odor on textiles.” In her ongoing research she hopes to identify the mechanisms for the interactions between odor molecule and fibers.

Textile science has taught has this: if the cutie from your running club invites you on a Valentine’s Day Five Miler, accept without fear of a stench. Just by pass all the high-tech fabrics in your drawer (at least for the layer closest to your skin) and don some cotton. Happy Valentine’s Day!

Image: elbow patch - HonestlyWTF, Photomicrographs: Fiber Reference Image Library