Why Cotton Can Kill You on a Hiking Trip
Cotton Kills Hikers
If you haven't heard the outdoor adage "cotton kills," pay attention and you may just save your life. Sure, cotton is fine to wear while shopping for groceries and looking "outdoorsy," but wear it in the great outdoors and it may kill you.
Every outdoor organization from the Boy Scouts to The Mountaineers warns vehemently against wearing cotton while hiking and backpacking. Despite multiple warnings from these experts, people perish each year from inadequate preparedness whilst in pursuit of outdoor adventure.
A guide friend of mine is so anti-cotton that he inspects each garment of everyone he is taking into the backcountry. He's been known to say, "take in an ounce of cotton, and pack out a cold body." A bit dramatic, yes—but is it well founded?
While teaching backpacking classes, my favorite illustration of the dangers of wearing cotton is to soak two pairs of pants—jeans and supplex hiking trousers—and let them sit out overnight. In the morning, the class gasps as the jeans creak and moan as I bent their frozen form in half. Meanwhile, I just shook the ice crystals off the hiking pants.
So which would you rather wear?
Cotton by Other Names
- 50/50 blends
Hypothermia: How Cotton Kills
Wearing cotton doesn't leach dangerous chemicals into your skin or make you more prone to being mauled by a rabid beaver, it kills through hypothermia. Hypothermia is a condition in which the body's temperature falls below 95 degrees; it results in death when untreated.
Most people think that hypothermia only happens while digging through five feet of snow, but often it occurs to unsuspecting hikers during marginal weather in the warmer months. According to Mountaineering First Aid, "Many hypothermia cases are reported in wet, windy weather with temperatures well above freezing."
Winter backpackers are usually prepared to combat freezing temperatures with multiple layers of technical clothing. Conversely, summer backpackers and hikers often skimp on warm extra layers and may wear inappropriate clothing that dries slowly and loses its thermal properties (cotton).
Wetness Equals Death
The major problem with cotton is that its hydrophilic nature causes it to dry very slowly and absorbs moisture like a greedy sponge. Conversely, materials like synthetics and merino wick moisture away from the skin and to the outside of the garment, where it evaporates.
So what does it matter if your cotton shirt is soaked?
According to the Appalachian Mountain Club, some forms of cotton absorb up to 27 times their weight. As a backpacker, you need to think carefully about anything that gains weight while outdoors. Like I said, cotton is a sponge.
Wet clothing conducts heat away from your body 25 times faster than dry clothing, so wet clothing (that favorite t-shirt of yours) is a recipe for contracting hypothermia.
Cotton: It's comfy when dry,
And cheap to buy.
But to wear it in winter,
It's a good way to die.— John Dunn, "Winterwise"
Rain Droplets on Cotton
Rain Droplets on Synthetic Shirt
Loss of Thermal Properties
Cotton is an outstanding insulator while it is dry; that's probably why we love flannel sheets on our beds. However, once cotton becomes wet, it loses 95% of its thermal properties, yes it will make you colder, a lot colder.
On the other hand, most specialty hiking clothing retains its insulating properties while it is wet. I've been submerged in streams slightly above the freezing point, but was fine due to the technical clothing that kept me warm while wet.
If you do insist on wearing cotton while hiking, you should carry several additional layers to change into when your clothing becomes soaked.
Hoodies Are Most Often Cotton
In a survey of my local outfitter, I found that 90% of hoodies are made of cotton. This is unfortunate, because the hoody is a favored garment for warmth, especially amongst the younger crowd. If you love the style, check out Under Armor's synthetic hoody selection.
What Happens to Jeans When They Freeze
When to Wear Cotton
Besides wearing for casual use, does cotton have a place in the outdoors?
Many desert hikers extol the virtues of cotton while trampling through arid climates. The sweat from their body soaks the cotton shirt and the gradual process of evaporation cools their bodies during the day. As the cool desert night air drifts in, hikers switch to dry clothes to avoid hypothermia.
Still other desert dwellers dislike the clammy feeling of wet cotton as they hike, so they prefer to wear synthetics. Though cotton has great UV blocking qualities, many treated garments like Omni-Shade from Columbia are better than cotton at protecting you from the sun. Even the Skin Cancer Foundation recommends those sun blocking materials.
Comfortable Alternatives to Cotton
Though some people like to wear cotton because "it is comfortable," they haven't worn some of the newer materials which are more comfortable, wick better, and dry faster.
A synthetic hiking shirt is an awesome thing to have, though some people will balk at the expense. I've had one shirt from The North Face that has lasted over 16 years. It thru-hiked the Appalachian Trail with me, climbed mountains, and bike toured across two states. Talk about rugged construction.
Currently my favorite shirts are the Wicked Light shirts from Mountain Hardwear. It is awesome to hike all day and have a dry shirt at the end of it.
- Merino Wool
In the early days of hiking, trekkers clad themselves from head to toe in wool—a renewable fiber that retains most of its thermal properties even while wet. As synthetics grew in popularity, people ditched the itchiness and weight of wool.
However, then companies started using Merino wool, a non-itchy super-comfy wool which keeps you warmer in winter and cooler in summer. Though many people love Merino socks (myself included) my favorite long-sleeved shirt is made from Merino by SmartWool. I have worn it for days at a time.
Cocona comes from the husks of coconuts. Now that sounds comfortable doesn't it? Actually it is. After coconuts are shelled, the husks are converted into activated carbon (also used for water filters) and then bonded to fibers for use in clothing.
Cocona products are very soft and comfortable, plus they have excellent technical benefits. I've found that my shirts made with cocona dry faster and have better moisture management than most other hiking shirts. Though antibacterial treatments can wash off, cocona's benefits are renewed when you wash them, which makes it a very sustainable garment.
My Favorite Hiking Shirt
A Few Examples of Tragic Outdoor Deaths
Nobody ever said hiking was safe, but here are a few examples of hikers who perished in the wild. Wearing cotton clothing seems to be a factor in each unfortunate example.
In September of 2008 a hiking party on the Pacific Crest Trail near Tinker's Knob encountered rain and high wind speeds, despite a sunny start to their trip. One hiker died and three others were rescued. A responding SAR team representative credited the tragedy with, "They had gotten separated, and they were wearing cotton, which takes forever to dry." (Source: "Exposure suspected in death of Pacific Crest Trail hiker" by Barbara Barte Osborn.)
One of the earlier examples from the Adirondack High Peaks happened during a tragic Thanksgiving weekend. Despite having a new compliment of "appropriate gear," two hikers were clad in all cotton. After getting waterlogged in an overly ambitious pursuit, an exhausted hiker with soaked cotton clothing succumbed to a hypothermic death before help could arrive. (Source: "Thanksgiving Weekend Death in the High Peaks" by Princeton Outdoor Action.)
In September 2005, a man hiking in the Alaska Range near Fairbanks died from the effects of hypothermia. A State Trooper was quoted, "He was wearing all cotton, which is the worst fabric for cold, wet weather. ... The weather just got the best of him." (Source: "Body of Wyoming Hiker Recovered From Alaska Range," AP.)
A Simple Hiking Clothing Experiment
So I read the accounts and experienced the lack of comfort in cotton-clad hiking, but was there a quick experiment I could do?
I glanced at the rain droplets gathering on my kitchen window and had an idea. I took two shirts, one lightweight cotton and one synthetic, and placed them on my lawn in a light rain. I let them sit for 40 minutes for a good old-fashioned soaking.
I wrung out both shirts as best I could, hung them on a line in an unheated area of my basement, and watched them dry. Watching a couple of shirts drip dry is slightly more exciting than waiting for the grass to grow, but a sacrifice in the name of "science."
The Mountain Hardware Wicked Lite synthetic shirt was dry within 3 hours.
The cotton t-shirt, a giveaway from National Trails Day, took 6.5 hours to dry.
The verdict: specialty hiking clothing dries more quickly than cotton. Given the facts that wet clothing creates heat loss and that cotton loses thermal properties while wet, cotton seems to be the loser in my mini-experiment.
A Comfortable Hiking Clothing System
So what do I wear for three-season hiking in the Northeast?
I always think of clothing as a system, and as the most technical part of my gear. This is generally what I carry.
- Shell Jacket: The North Face Verto (water and wind resistant)
- Warmth: EMS microfleece (zip neck)
- Shirt: Mountain Hardware Wicked Lite t-shirt (one every three days)
- Pants: EMS Supplex convertible pants/shorts
- Shell Pants: Sierra Designs Microlight windpants
- Boxers: Ex Officio Give 'n Go boxer briefs (one every two days)
- Socks: SmartWool medium hiking socks (one pair per day)
- Warm hat: Mountain Hardware neck gaiter
- Glove: Seirus Hyperlite gloves
So Will Cotton Actually Kill You?
Before accusing me and the entire outdoor industry of sensationalist hyperbolic claims, let's look at cotton one more time.
The fact is, many new and old hikers alike venture into the wild with cotton clothing and return unscathed. However, wearing non-cotton clothing is safer.
As part of risk management, you can't eliminate all risk, but you can make things safer. Surely, nobody plans on twisting an ankle or taking the wrong trail, but you can plan what you wear. You will have a safer and more comfortable time in the outdoors if you wear non-cotton performance hiking clothing.
© 2012 Dan Human