If you have hiked for long enough, you would have heard the age-old adage that cotton kills. Of course, the cotton itself won’t kill you – it is not poisonous and does not attract bears – but rather that wearing cotton can lead to hypothermia.
But are there any exceptions to this rule, and is cotton good for hiking under certain circumstances?
Unless hiking in hot climates with no chance of environmental extremes, then cotton is not a good choice for hiking. It is a highly absorptive material that can take in up to 27 times its own weight in water. It is heavy, slow drying and loses all of its insulation properties when wet.
How the saying “cotton kills” came to be
“Cotton kills” is one of those things that creep into a language and sticks. It is catchy, rolls off the tongue and carries with it a certain truth.
Over the years countless hikers have lost their lives because of a poor choice of attire. “Cotton kills” has become almost a cliche due to the sheer volume of people who have perished in the wild because of their cotton-clad bodies.
In New Zealand I recently saw national park rangers turning around would-be trekkers who were wearing cheap sneakers, jeans and cotton shirts. I waited and asked the ranger a few questions. They were tired of having to rescue – and in some cases recover the bodies – of those heading into extreme environments without the right gear.
Why cotton is bad for hiking
There is no one answer for this, but rather that one thing leads to another. To get to the bottom of it we need to discuss the wicking and insulation properties of cotton that, under the right circumstances – are conducive to a hiker succumbing to hypothermia.
Naturally absorbs water:
When discussing hiking clothes, you may have come across the term wicking. This is simply the transfer of moisture from your body, through your clothing and out into the atmosphere. Certain materials are super-efficient in the wicking process. Cotton is not one of these.
It comes from a plant. While growing, the cotton fiber is cylindrical in shape and is filled with living cells. After the plant matures, the cells dry up and that cylindrical shape contracts. Once made into an item of clothing and exposed to water, these tube-like fibers absorb and retain that water.
Decent insulator when dry but terrible when wet:
When dry, cotton provides decent insulation via those trapped air pockets we were talking about. When it becomes wet, those tubes fill up with water, and all that insulation goes out the window.
Water has the ability to impact on the body up to 25 times more than that of air. Therefore, you do not even need to be in particularly cold weather to succumb to hypothermia. Sometimes even when the temperature is in the 90s, a cool breeze is all it takes to send shivers down the spine.
Synthetic and other hiking-friendly fabrics such as merino wool (more information below) do not lose their insulation properties, even when wet.
Cotton multiplies your chances of getting hypothermia:
It is a dangerous situation to get yourself into. Hypothermia officially sets in when your core body temperature drops below 95oF. When at or below this temperature, the organs in your body are unable to function properly. You heart does not pump as efficiently and your nervous system takes a battering.
If you keep your body in this state for too long, it can lead to the complete failure of your heart and respiratory system, and eventually death.
A hiker may not consider wet clothing to be a problem while they are on the move. Climbing up hills and mountains, negotiating difficult terrain and carrying stuff on your back can cause your body temperature to rise dramatically.
However, there are a number of things that can happen to change this all too quickly:
Weather – A sudden increase in wind speed can lower your body temperature in seconds. As can a sudden unexpected drop in temperature, something that should be expected in mountainous environments. The wind and the cold combined with your wet clothes could land you in a world of trouble.
Rest breaks – It can be quite amazing. One second you are overheating, the next you are shivering through the cold. Once hikers stop moving, it is surprising just how quick your core temperature drops.
Descending – Soaking wet from the climb and then being forced into a descent changes the way the body works. Although taxing on your legs and knee joints, descents tend to lower your body temperature, as far less exertion is required with gravity on your side.
Injury – They are unexpected occurrences, which is why they are also called accidents. If you happen to find yourself injured, alone and unable to move with wet clothing on, it could very well be the end of you.
Elevation gains – There will come times when even the laborious slog up a steep slope will not be enough to keep you warm. The higher you climb, the lower the temperature falls (more so the further you get from the equator). If you are already wet, still climbing and becoming uncomfortably cold, it is time to turn around an lose some altitude.
Fatigue – This is unfortunately a bit of a double-edged sword. On the one hand, being in a fatigued state will naturally slow down your output of energy. This in turn means you move slower and less efficiently, which can cause your body temperature to drop. There are also medical links between feeling tired and cold, so by simply being fatigued you are more likely to feel the cold.
Exceptions to the rule, when to wear cotton:
Sometimes people choose to do their hiking in hot desert environments. These regions can be stunning in their own way. They often come with rolling sand dunes and extra-terrestrial landscapes. It can feel more like you are on the surface of Mars than the lush green-and-blue of planet earth.
Hot and dry environments
In these hot, dry environments it can be particularly rewarding to hike in light cotton t-shirts. The heat, although dry, will cause the body to sweat. The sweat is absorbed and retained by the cotton fibers, which in turn has the capacity to keep hiker’s cooler during the hottest parts of the day.
As desert environments are prone to extremes of temperature, often the mercury will drop below freezing at night. It is recommended to hike in cotton during the day (or a cotton/ synthetic blend), and switch to dry and warmer clothes in the evening.
This can also apply to hot, humid weather, such as that experienced in tropical environments. Cotton allows the air to flow around your body, which will lower your body temperature.
Hiking in jeans? Leave them at home…
Jeans are made from denim and denim is made from 100% pure cotton. So the predictable answer here is that jeans are not a good choice for hiking. In fact, you would be hard-pressed to pick a worse style of pants to wear.
So, everything that we have already covered with cotton is applicable to the jeans you are wearing. They absorb water about as efficiently as your towel and take about as long to dry. They can feel too cold in winter and too hot in summer.
Although not in the same ball park as hypothermia, wearing jeans on the trail can lead to serious levels of pain and discomfort. After wearing jeans for an extended period of time, the coarser material can rub your skin red-raw. This chaffing is particularly common between the legs and it can be exceedingly uncomfortable.
When it comes to hiking it is all about layers. Look for pants that are predominantly nylon-based and have been given some kind of water-resistance treatment. If it is too cold, wear a pair of merino-based thermal pants underneath. If it is wet, wear a pair of waterproof pants over the top as part of your outer waterproof shell.
Read more on accidental hypothermia in the backcountry here: onlinelibrary.wiley.com
What kind of shirt should I wear hiking?
Merino wool comes from a certain breed of sheep, and is an exceptionally good choice for hiking. It is the ideal material for base layers, socks and t-shirts. It is soft, light, breathable, comfortable, warm and cool.
That may sound like a contradiction, but it is not. Merino comes with natural creases in the fiber that are able to trap heat up against the body. It is also completely breathable, which means that it can easily release heat as well. Think of those sheep in the summer months. They would succumb to heat exhaustion if the heat could not escape.
It makes merino the perfect body temperature regulator for next-to-skin clothing. Another amazing thing about merino wool is the naturally anti-bacterial nature of the fibers. This means that it actively reduces the bad body odors caused by physical exertion. You can wear your merino hiking shirt for days before you start to gain unwanted smell-related attention.
It also has high moisture wicking capabilities, and retains its insulation properties, even when completely wet. The only downside of this product is its durability. The fabric is not the strongest and tears easy on abrasive surfaces.
Up Next In Hiking Gear: