Does Cotton Clothing Kill Hikers?

Killer T-shirt?
Killer T-shirt? | Source

Introduction: A bittersweet hiking story

Several years ago, I participated in a Sierra Club sponsored day-hike in the Desolation Wilderness, just a bit West of Lake Tahoe. During a break, the leader made a snotty comment about my cotton shirt and trousers. Apparently clothing made from synthetics and/or wool is now de rigueur in some Greenie circles. Just what I always needed: the Outdoor Fashion Police!

I can still remember the good old days, when all Sierra Club leaders had good manners, and were considerably less militant about everything. Anyway, that's the backdrop for this hub.

Hikers are very much concerned with staying warm on their outings. To a large extent, that means staying dry. A wise choice of outdoor fabrics can help you to stay both warm and reasonably dry.

Is the fabric in your hiking shirt a 'magnet' for water?

That depends on the material, and on the tightness of the weave. In our exploration of that question, we'll use expressions like condensation, dead air spaces, ester linkages, hydrogen bonding, hydrophilic, and vapor barrier. Notwithstanding some arcane terminology, I'll try to keep this hub accessible.

When you're warm and dry, other aspects of comfort come into play. And it's much more difficult to make generalizations about comfort that apply to everyone. Some shirts are made from synthetic fabrics that are designed to help you feel cool in hot weather. And in that respect, they work for some people, but not for others.

For some, a big part of feeling cool on a hot day is not having visible perspiration under the arms of their shirts. A shirt with a high polyester content will be a good choice if that's a major consideration.

For others, wearing a high-polyester shirt on a hot day is slightly uncomfortable in its own right. I fall into that category.

The basic functions of outdoor clothing are to keep you warm, dry, shielded from excessive sun exposure, and to keep the mozzies (mosquitoes) away from your skin. Once the basic requirements are met, there's a large amount of subjectivity that enters into your selection of a fabric in your outdoor garments. What's comfortable for me, does not necessarily work for everyone. And sometimes there are trade-offs between functionality and comfort.

How do you feel about cotton as an outdoor fabric?

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Pyramid Lake in Desolation Wilderness
Pyramid Lake in Desolation Wilderness | Source
Ester linkage
Ester linkage | Source

The lowdown on outdoor fabrics

Many outdoors people hold the opinion that cotton kills. And there's a kernel of truth in that saying. If you're caught out in the open during a sudden mountain rainstorm on a cold day, you're at greater risk of hypothermia if you wear cotton clothing, as compared with wool or most synthetics. What's up with that?

Cotton is mostly cellulose, which has a relatively high proportion of electronegative (electron-withdrawing) oxygen atoms. When an oxygen atom is bonded to a carbon atom, it acquires a partial negative charge, due to unequal sharing of an electron pair--or two electron pairs--with the carbon atom. A hydrogen atom in water has a partial positive charge for the same reason. The hydrogen atoms in water form "hydrogen bonds" with these oxygen atoms in cellulose. Once hydrogen bonds form, energy is needed to cleave them apart.

The structural formula at right shows one of the repeating ester linkages in polyester. In between these linkages, there are relatively short carbon chains (R and R'), with hydrogen atoms attached. In contrast with the ester linkages, these chains don't attract water. As compared with cellulose, polyester has a relatively low concentration of water-attracting oxygen atoms.

The upshot: Cotton attracts water more readily than polyester does. It requires slightly more energy to evaporate the water in a damp all-cotton shirt than the same amount of water in a wet polyester shirt.

More to the point, cotton fabric can hold more water than polyester.

Here's what happens on a vigorous mountain hike. At first, the cotton shirt will decrease the evaporation rate of your perspiration. Initially, this will slow down the rate of heat loss.

But as you continue hiking, the perspiration will clog up an increasing proportion of the fabric's dead air spaces that create the warming effect in the first place.

Layering advocates are definitely on target. Two wool layers are warmer than an extra-thick single layer, having the same weight. Why? Because there's some dead air space between the two layers, and more dead air space overall. Moreover having multiple layers allows you to get the right amount of insulation for your exertion level, and for the outside temperature. Then you won't perspire as much, and won't degrade the dead air spaces in the insulating layers.

One nice thing about a wool sweater is that even when it's wet, there are still a few dead air spaces to keep you warm. Ditto for the synthetic material, polypropylene. However the latter can get pretty stinky if you wear it next to your skin every night on a long backpack trip.

There are pros and cons for cotton as an outdoor fabric. I have sensory issues, and feel uncomfortable when I'm wearing too much synthetic fabric.

Work pants are somewhat better than blue jeans. The fabric is thinner, which means that it dries out faster after you get rained upon. Some work pants are all-cotton; others come in a cotton/polyester blend.

A word about fire safety. Suppose that a spark from the campfire lands on your shirt. The spark will burn a bigger hole through synthetic fabric, as compared with cotton fabric. When sitting near a campfire, it would be reasonable to wear a long-sleeve cotton shirt on the outside, with your synthetic fleece on the inside.

On hikes, there are advantages and disadvantages to both cotton and synthetic fabrics. The "Cotton kills" meme is an exaggeration. It applies more to long backpacking trips than to day-hikes, and more to the North Cascades and Rocky Mountains than to the Sierras.

For some, a reasonable trade-off is to hike in an old permanent-press shirt, which contains both polyester and cotton. Compromise is not a four-letter word.

Retro Larry hiking in his cotton shirt
Retro Larry hiking in his cotton shirt | Source

The wicking myth

The sales people at hiking-oriented sporting goods stores are fond of another urban legend about outdoor fabrics. They say that polyester and other synthetic fabrics 'wick' moisture away from your skin, whereas cotton does not. This claim is inaccurate. "Wicking" is a vacuous marketing slogan that's taken on a life of its own.

Again, cotton fabric contains a higher density of hydrophilic groups than polyester.

Other things being equal, cotton is more efficient at wicking water away from your skin in the short term, especially in the uphill direction.

The catch is that the same cotton fabric will hold more moisture than polyester fabric. The water in that sweaty cotton fabric will take longer to evaporate. Sorry, you can't have it both ways.

Fishnet undershirt

I usually carry a small rucksack on hikes. If it's a vigorous uphill hike, there will be a wet perspiration spot on my the upper back part of my shirt, when we stop. I'll feel a sudden chilliness when I take off the rucksack. But that was not always a problem.

Many years ago, I had a wonderful fishnet undershirt, made from--you guessed it--Killer Cotton. Because of the semi-dead air spaces, it prevented the upper back part of my outer shirt from getting soaked with perspiration.

After my trusty fishnet finally gave up the ghost, I looked at some of the newer ones. They're part fishnet and part ordinary T-shirt. Apparently the manufacturers have lost sight of the original concept.

The answer to your next question is no; fishnets are not comfortable to wear while sleeping.

Lake Tahoe
Lake Tahoe | Source

What to do when it rains?

A little-known fact about California hiking is that Summer weather is drier in the Sierras and in the Trinity Alps, than in the Rockies and most other Alpine environments. (The Trinities are NNW of the Sierras.) On day-hikes here, one can get away with wearing cotton clothing. And I do.

Nevertheless it's wise to carry emergency rain gear, even when the weather forecast is favorable.

Some cheapskate day-hikers in California make do with an ultra-lightweight option for rain protection: a plastic garbage sack, with precut holes for the neck and arms.

For the last few decades, some very nice rain parkas, made with Gore-Tex and similar materials, have been available. Basically, Gore-Tex is teflon with zillions of micropores. Rain cannot get through the micropores. However gas-phase H2O from your perspiration can slowly escape to the outside. The key word is slowly.

In the days before Gore-Tex, many anoraks were made from very-tightly woven cotton, which made these jackets wind-proof, and somewhat water-repellent, but not waterproof. One advantage of the old-school anoraks, and of the modern wind shells, is that they breathe out moisture more readily than Gore-Tex rain jackets do. If you're hiking vigorously in a light drizzle, and you perspire as heavily as I do, you'll get wet faster with Gore-Tex, because of the 'breathing' issue.

On the other hand, if you get caught in a heavy mountain downpour, and then take partial shelter under a tree while waiting out the storm, you'll keep drier longer with Gore-Tex, because Gore-Tex does keep the outside moisture outside.

In either case, once the outside material is completely wet, your evaporated perspiration will condense on the inside, and your shirt and sweater will become increasingly wet. Continuing to hike vigorously will hasten that process.

If you plan to hike even when the weather forecast calls for rain, there are three options. First, you can wear a polyester (or polypro) undershirt next to your skin, one or two wool layers over that, and a wind shell as the outermost layer. Yes, you'll get wet, but you will probably avoid hypothermia. This is the strategy favored by some hard-core climbers.

Second, you can carry a small umbrella. The upper half of your rain jacket will still be breathing, and that will cut down on the condensation. It will also decrease the amount of rain hitting the upper-front part of your trousers while you're hiking.

Yes, the umbrella looks wimpy. It's a nuisance to tilt it out of the way when you approach tree branches that are less than 2m high. And carrying an umbrella is not very practical in a high wind. This option applies mostly to trail hiking. The umbrella gets in the way when you're bushwhacking. Fortunately, there's a better option.

Another scene in Desolation Wilderness.
Another scene in Desolation Wilderness. | Source

Vapor barrier, anyone?

There's a third strategy in the rainy-day scenario: Wear a Vapor Barrier Layer next to your skin, and a Gore-Tex parka, or even a cheap lightweight plastic raincoat, over the insulating layer.

There's no way that the insulating layer can get wet. The Vapor Barrier protects the insulating layer from sweat. And the Gore-Tex parka protects it from the rain. (You may need to apply some seam-sealer to your parka.)

The hem of the rain parka should extend below your hips. A drawstring at the waist will help keep the warm air inside the parka.

You can easily make a torso-covering Vapor Barrier Liner from an inexpensive plastic Tall Kitchen Bag that's available in any supermarket. Just cut holes for the neck and arms.

If you have a full vapor barrier for your torso and arms, you can even even use Killer Cotton as the insulating layer between the vapor barrier and the rain jacket. The Outdoor Fashion Police may have hissy fits, but you'll stay warm and dry.

A caveat about the Vapor Barrier strategy: You may need to go slow on the uphills to avoid overheating, if it hasn't started raining yet.

By the way, if you're camping out in sub-freezing weather, and the air is relatively dry, you'll notice frost on the outside of your sleeping bag when you get up in the morning. You'll also notice that there's no frost anywhere else. That's because your body was the ultimate source of that frost. Your sleeping bag will become heavier and chillier each night, for the same reason. To minimize this problem, you need a Vapor Barrier Liner (VBL) for the sleeping bag.

Stephenson's Warmlite, which was founded by an engineer, was the first manufacturer to offer a VBL as a standard feature in their sleeping bags. Here's a LINK to the long article in their catalog about the Vapor Barrier Principle. I agree with most of what they say.


There's a little more to the story at the beginning of this hub. First, it was a great hike in all other respects. Our destination was Susie Lake, in the Desolation Wilderness, just West of Lake Tahoe. And it was gorgeous.

There was another thing that made this a memorable outing. At lunch, one of the women hikers casually pulled a blue-and-silver-colored, banana-shaped object from her rucksack. We all held our breaths as she opened it. We were surprised and slightly disappointed that there were no batteries inside. Believe it or not, the object contained a banana!

I'd like to thank everyone for your comments. You've inspired me to improve this hub.

Lake of the Woods is also in Desolation Wilderness. From the Echo Lakes trailhead, this is a shorter hike than for the more famous Aloha Lake, but it's just as beautiful.
Lake of the Woods is also in Desolation Wilderness. From the Echo Lakes trailhead, this is a shorter hike than for the more famous Aloha Lake, but it's just as beautiful. | Source

Also of interest to mountain hikers

At Home Exercise to Strengthen Weak Upper Legs

This article describes a slow-paced indoor exercise, called Gorilla Walking. As compared with ordinary walking, Gorilla Walking does a much better job of isolating and strengthening the quadriceps muscles in the front part of the upper legs.
Upper legs

Copyright 2011 and 2012 by Larry Fields

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Comments 48 comments

A.A. Zavala profile image

A.A. Zavala 5 years ago from Texas

I hate snobs! Interesting facts about cotton. How fascinating...

Larry Fields profile image

Larry Fields 5 years ago from Northern California Author

Hi A.A. Zavala. Thanks for stopping by.

rich_hayles profile image

rich_hayles 5 years ago

Haha, what a random hub, fantastic!

Glad your hike went well and thanks very much for the information.

Larry Fields profile image

Larry Fields 5 years ago from Northern California Author

Hi rich_hayles. Thanks for your comment.

Kris Heeter profile image

Kris Heeter 5 years ago from Indiana

Very interesting. I hadn't heard the "cotton kills" saying before in reference to hiking. But when I spent some time in Kenya, the advice was "no cotton" for the some of reasons referenced here. In those temps and high humidity, cotton would just hold water.

Great hub - love the science you've discussed behind it.

Larry Fields profile image

Larry Fields 5 years ago from Northern California Author

Hi Kris Heeter. Thanks for sharing your experience in Kenya.

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Jim Holle 5 years ago

Great article! While I currently live in Florida, I have hiked and camped in the NW and have wondered and discussed the best types of clothing for outdoor activities. For the reasons that you suggest that cotton is a "killer," in the tropics would those qualities help keep me cooler? I have tried various technical clothing but find that cotton works great.

Larry Fields profile image

Larry Fields 5 years ago from Northern California Author

Hi Jim. Thanks for stopping by.

My only experience with tropical trekking was a short hike on Kauai. The only equipment shortcoming was the lack of a hiking pole. The trail had a thin layer of sloped and slippery mud on top of firmer material underneath. I'd never experienced anything like that before.

That said, your intuition about cotton in the tropics is probably good, assuming that there's no sudden temperature decline when the sun goes down.

On the other hand, I've heard that some guys in Hawaii don't even bother with umbrellas or rain jackets. They just wear an Aloha shirt that's high in polyester, and very low in cotton. On warm days, they dry off quickly when the sun comes out, and they experience negligible discomfort.

badegg profile image

badegg 5 years ago from Southern Appalachians

I spent many days/weeks/months hiking in the John Muir Wilderness and along the Pacific Crest Trail leading Boy Scouts up and down the trail and in canoes up and down the Colorado River. Remembering back to those days (1970's), the BSA uniforms were made of heavy cotton, and the older uniforms of the Scoutmasters were seemingly made of wool. But as you said, the cotton was of little consequence in the California weather.

But now I live in the lower Appalachians not far from the trail head of the Appalachian Trail, and weatherwise, wearing cotton in this humidity is an uncomfortable experience. Your article was well thought out and well written. Anyone who has never donned a backpack and set out for weeks on end in the wilderness (or even a day hike) would never understand your message.

Larry Fields profile image

Larry Fields 5 years ago from Northern California Author

Hi badegg. Thanks for your comment.

Melovy profile image

Melovy 5 years ago from UK

Interesting hub. I’d never heard the phrase ‘cotton kills’ before. I’m at most a day-trip hiker, so probably not qualified to give an opinion, but I have always found cotton to be cool and comfortable and polyester makes me sweaty and uncomfortable. I tend to do as you do, and wear cotton as an inner layer, wool if needed, and then goretex, because that way I am comfortable and dry.

I found this article to be very balanced and informative, and like Kris I appreciate you including the science. Thank you for the hub.

Larry Fields profile image

Larry Fields 5 years ago from Northern California Author

Hi Melovy. Thanks for stopping by.

Crude Oil Trader profile image

Crude Oil Trader 5 years ago from Tucson Arizona

Great post, I have been saying this for years and have my family wearing poly polypropylene even around the house. save a ton on utility bills in the winter. Unfortunately we can only find it in the military surplus stores since the military is about the only ones smart enough to still use it.

Larry Fields profile image

Larry Fields 5 years ago from Northern California Author

Hi Crude Oil Trader. Thanks for your comment.

thougtforce profile image

thougtforce 5 years ago from Sweden

Interesting article and I have always heard that cotton is the best material to wear because it lets the skin breaths! But I am not a person that usually do long hikes so maybe that is the reason why I prefer cotton. It sounds as if it is difficult to find the ultimate fabric in extreme situations. Great information about the materials and why it work, or not work!


Larry Fields profile image

Larry Fields 5 years ago from Northern California Author

Hi Tina. Sometimes I say too much. In trying to cover all of the bases, one can make a topic appear to be be more complicated than it really is. Thanks for your patience.

marshacanada profile image

marshacanada 4 years ago from Vancouver BC

I live on the wet west coast of BC and do a lot of hiking,back packing and I used to climb mountains-Because of our geography we can be out for days in rain,hail,sleet snow etc. Our clothing system for bottom is Polypro underwear long and short in several layers then quick dry nylon pants. Same material on top then fleece then gortex jacket.

If raining gortex jacket and pants and then if its driving rain a waterproof ponch on top.This works well in cool/cold wet weather as long as you take layers off when you warm up so you don't sweat too much and get soaked from sweat.

In hot weather-ie India, Egypt I have always hiked in loose cotton to protect myself from the sun.

Larry Fields profile image

Larry Fields 4 years ago from Northern California Author

Hi marshacanada. Thanks for sharing your experiences.

Jakebrap profile image

Jakebrap 4 years ago from Liverpool, UK

Massively interesting read :] was surprised I was so enthralled as this isn't usually the type of hub I'd read. Brilliant though!

Larry Fields profile image

Larry Fields 4 years ago from Northern California Author

Hi Jakebrap. Thanks for stopping by.

Jakebrap profile image

Jakebrap 4 years ago from Liverpool, UK

No problem!

natures47friend profile image

natures47friend 4 years ago from Sunny Art Deco Napier, New Zealand.

Very interesting and well written hub. I tend to wear a lot of cotton and only go on short hikes.

Your pictures are awesome too.

Larry Fields profile image

Larry Fields 4 years ago from Northern California Author

Hi natures47friend. Thanks for your comment. I wish that I could take credit for the pictures, but most of them came from Wikipedia. However Desolation Wilderness is an awesome place. My guess is that the pictures make themselves there.

Attikos profile image

Attikos 4 years ago from East Cackalacky

Read the literature, and you get the idea that a swatch of cotton within a mile of your campsite is deadly. The facts are a bit different. It's the characteristics of cotton clothing hikers need to know. It's absorbent, and once wet it stubbornly stays that way. It's a wet blanket, a moist cocoon surrounding your delicate bod, an evaporative engine. That's bad when it's cold because it makes you cooler, but it's good when it's hot because ... uhm ... it makes you cooler. Here in the Southern Appalachians, I use it all the time in summer, never in winter. Go figger.

Larry Fields profile image

Larry Fields 4 years ago from Northern California Author

Hi Attikos. Thanks for stopping by. You're right. Sometimes the shrillness of the rhetoric can be quite revealing. I'm reminded of Benford's Law of Controversy:

"Passion is inversely proportional to the amount of real information available."

marshacanada profile image

marshacanada 4 years ago from Vancouver BC

I am going hiking and back country camping into Yoho Park this week-next to the Banff Rockie Mountain ranges. I amWishing for sunshine but taking my long poncho, lots of Gortex rain gear and polypropelene and fleece.

Larry Fields profile image

Larry Fields 4 years ago from Northern California Author

Hi marshacanada. Nice to hear from you again. I hope that you enjoy your trip.

nurlyla 4 years ago

thanks for the great article.

Larry Fields profile image

Larry Fields 4 years ago from Northern California Author

Hi nurlyla. Thanks for stopping by.

bjorn 4 years ago

JP Muller is worth a read. And Robert Jackson "How To Be Always Well"

Mr. Davis 4 years ago

I like hiking. It's real good

Larry Fields profile image

Larry Fields 4 years ago from Northern California Author

Hi Mr Davis. Thanks for stopping by.

David Warren profile image

David Warren 4 years ago from Nevada

LOL and great hub! I've been hiking the Tahoe Rim Trail in Levi's and cotton shirts for over a decade and lo and behold, I'm Alive!!! Your hub was very informative and interesting to read. Voted up!

Larry Fields profile image

Larry Fields 4 years ago from Northern California Author

Hi David. Thanks for your testimonial on the safety of cotton. :)

Efficient Admin profile image

Efficient Admin 4 years ago from Charlotte, NC

In one of my hiking groups the leader is adamantly against cotton clothes for the longer mountain hikes. I have noticed if I wear polyester clothes I don't get hot as quick, or at least the sweat evaporates quicker. Thank you for sharing this informative and useful information. Voted up.

Larry Fields profile image

Larry Fields 4 years ago from Northern California Author

Hi Efficient Admin,

East Coast hiking weather is different than that of the Sierras. Since Summer showers are much less common here, we can get away with being more casual about our hiking attire.

Thanks for stopping by.

Efficient Admin profile image

Efficient Admin 4 years ago from Charlotte, NC

Hello Larry - I hear your humidity is not as horrid as ours. The humidity is so bad here in July and August, most people just stay inside the air conditioning during those months. You have to drink lots of water or get dehydrated really quick in this humidity here.

Larry Fields profile image

Larry Fields 4 years ago from Northern California Author

Hi Efficient Admin,

Yes, it's true. As Arizonans say, it's a dry heat. And during the Summer, it's easy to escape the Central Valley heat. When it's 100° here, it'll only be 75 up on the hikes in the Carson Pass area.

Nell Rose profile image

Nell Rose 4 years ago from England

Hi Larry, to be honest if I could walk those trails where you go I would wear anything, they are amazing so much better than the walks over here! lol! as for cotton, well I never! If I could remember what you said about the water content plus the energy etc I would sprout it about everywhere trying to make myself look clever! haha! great read, and yes I have done that too! the plastic bin bag with the holes in the neck and arms, I went to work on my pushbike it was pouring with rain when we finished work so I stole one from work! it was great! as snug as a bug in a rug as my mum would say! lol!

Larry Fields profile image

Larry Fields 4 years ago from Northern California Author

Hi Nell. Thanks for stopping by.

Phil Fischer 3 years ago

Nice content! Another component to the issue is wind and dewpoint. The temperature of loose wet cotton will approach the dew point. If the air is very dry, the dew point can achieve the freeze point. If raining, no evaporation takes place, and therefore no cooling.

The Sling psychrometers are based on this principle. From a molecular point of view, water molecules continuously break free into the air and in the process cool the remaining water by removing latent heat by the phase change. Water molecules in the air in gas phase also are recaptured by the water. An equilibrium occurs when an equal number of molecules change phase in each direction. Moving the air brings in drier air, reduces the recapture rate, and lowers the water temperature.

So the bottom line is that cotton (or any material) can feel very cold on a beautiful blue sky day if the humidity is low.

Larry Fields profile image

Larry Fields 3 years ago from Northern California Author

Hi Phil. Thanks for stopping by.

dionm profile image

dionm 3 years ago from Somewhere on Earth.

Larry, you've got a great style. I found the whole chemistry perspective novel and a most entertaining read. Thanks and I look forward to reading more of your work.

Larry Fields profile image

Larry Fields 3 years ago from Northern California Author

Hi dionm. Thanks for stopping by.

Mel Carriere profile image

Mel Carriere 3 years ago from San Diego California

Interesting take. I had no idea that fabric choice was a factor on hiking expeditions. I have been enlightened!

Larry Fields profile image

Larry Fields 3 years ago from Northern California Author

Hi Mel. Thanks for your comment.

Robert 3 years ago

The whole "cotton kills" is usually when inexperienced hikers don't prepare properly, or for ignorant hikers who think they're invincible to the elements. I bought my last hiking clothing at and they guy in stores advised against ever wearing cotton clothing when backpacking or hiking and I'm glad I took his advice. Last hiking trip in Scotland it poured most of the time and with synthetic clothing even though was wet, didn't cause as much damage and was easier to dry.

Larry Fields profile image

Larry Fields 4 months ago from Northern California Author

Hi Robert. Thanks for stopping by. Apparently, the weather in Scotland is much wetter than in the Northern Sierras of California, where I like to hike

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