Is "Cotton Kills" Outdated Advice for Outdoor Adventure?

When I first began to explore the great outdoors on childhood adventures, one of the most prevalent adages I heard was “cotton kills.” It invoked images of a predatory cotton monster lurking behind the next boulder, ready to leap out and tear me apart with its absurdly soft and breathable fangs. Later on, as I took Outdoor Leadership Training and received my Wilderness First Aid certification with the Appalachian Mountain Club, that same adage was repeated by course instructors, as if this bit of information would one day save lives on our two-mile round-trip hike in 75 degree weather. I repeated this phrase many times to my own students, parroting the advice I’d received, though it is only recently that I’ve begun to question the accepted wisdom.

I don’t mean to downplay the dangers of cotton in specific conditions. Cotton absorbs moisture, insulates poorly when wet, and dries slowly, increasing the risk of hypothermia. Rest assured, cotton is a bad choice when engaging in high exertion activities in frigid weather, and the consequences can be deadly. Yet how many of us weekend warriors routinely go on that kind of adventure? We don’t advise flag football players to don pads every time they throw the pigskin around, but we sometimes act like a walk in the woods requires a professional level of gearing up.

Of course, I love gearing up for the same reason many people love wearing a Patrick Mahomes jersey in daily life. I’m often decked out in synthetic layers like fleece or polyester that have high performance attributes—they shed moisture and dry quickly—but that are also made from petroleum-based materials and shed micro plastics into the natural environments I visit (not to mention my own home). “Cotton kills” is so alliteratively catchy that you could tell me it was invented by Big Oil to encourage the proliferation of plastics and I wouldn’t bat an eye.

It was while interviewing Brice Partouche, the founder and Creative Director of the running brand Satisfy, that I became intrigued by cotton as a performance fabric. Partouche mentioned the brand's MothTech line, which features perforated organic cotton tees. “Runners have been told for decades that they can’t run in cotton and have to wash their running gear after every run,” said Partouche. “We can’t disagree more. Our pro athletes wear our organic cotton and merino on ultras without any complaints.”

In the cotton-averse world of performance apparel, this was like admitting that Satisfy used sandpaper in its production process. However, cotton is renowned for its breathability. It's a natural material and, like wool, it's biodegradable, allowing for a circular production process. Merino wool has long been a preferred performance layer thanks to its ability to act as a natural insulator, its antimicrobial properties, and its ability to remain warm when wet and dry quickly. The knock on cotton is that it absorbs moisture, causing it to become wet and heavy when soaked through.

Yet a comprehensive meta-analysis on thermoregulation, comfort, and performance during sport points out that some studies have shown no benefits from wearing polyester compared to cotton. Other studies, they wrote, “have reported significant reductions in core temperature, skin temperature, sweat loss, and heart rate when wearing cotton clothing during exercise compared to synthetic fabrics.” The researchers also highlighted the significant improvement in “thermal sensation” of cotton in hot and dry conditions.

In other words, cotton feels good. Perhaps this is what the mountain biking performance apparel manufacturer Curious Creatures recognized when it decided to make an MTB layer out of plain old cotton. The description for the Cottonwood Long Sleeve Tee—which I can attest is both soft and groovy—reads, “We believe in the ineffable comfort of natural fabrics…We find ourselves reaching for them again and again and although lab data shows that plastic ‘performs’ better there is something to the soul of naturals against your skin that can’t be described in numbers.” Maybe it's time we trust our own thermal sensation.

Other brands have started expanding their cotton offerings for sustainability reasons, marketing it as the ideal fabric for travel and daily rigors. Organic cotton uses less water, fertilizer, and pesticides, and can contribute to better soil health. Roark’s Well Worn line and Stio’s Whitebark collection are both made of organic cotton that is perfectly suited to light trail duty. Topo Designs' Dirt Collection is so named both because with it, the company aims to reduce dirty cotton production by using organic cotton, and because the hint of stretch and durability of the long-weave fibers means these garments are intended to get dirty.

If you're planning a high-exertion outing in an environment with the potential to get cold, don’t go with cotton. But if you are like me, cotton will be plenty capable and comfortable for most of your excursions, with the added benefit of being better for the environment, especially if it's organic. Perhaps it's time to kill that old, well-worn saying—“cotton kills”—and to instead educate others on the performance and provenance of all fabrics. The cotton monster only exists in our heads.