Does cotton kill? Not in the desert!
There is a great debate in the outdoor recreation circles - whether or not to wear cotton or synthetic clothing when participating in sweat producing activities outside. This clothing controversy must be addressed as it is a very important topic if you are planning a hike here in the Southwest in the late Spring, Summer and early Fall.
Many outdoor enthusiasts, especially those who live in cooler and wetter climates believe that wearing cotton is one of the worst things you can do while engaging in outdoor activities. This is because as you sweat, cotton stays moist longer, thus zapping body heat from your body. But think about this premise in a climate where the humidity may get as high as 14% with temperatures of 115 degrees F in the shade. Do you want to preserve body heat? NO! You want moisture to keep you cool, and the longer you can stay wet, the better. As the moisture evaporates from your clothing, it cools your body as well. As perspiration evaporates, it cools your blood that is closest to skin level and circulates the cooler blood throughout your body - keeping your core temperature at its ideal 98.6 degrees F. Think of the last time you stood in the mist of a waterfall. The air surrounding the mist has a chill. As the mist evaporates, it cools the air around it, not vice versa. However, wicking material pulls this much-needed moisture away from the skin, allowing the material to dry quicker while also keeping your skin dry - and hot. This may be more comfortable when hiking in cold and/or wet climates, but is not ideal when exposed to the hot, desert sun.
What should you wear? Denim is cotton, but don't wear that. A cotton t-shirt that you can get wet often is sufficient in keeping the core of your body cool. Let's take the Grand Canyon for example. You can go on a Grand Canyon hiking trip year round. In the Winter, wicking materials are a good idea as it does also snow at Grand Canyon and a normal Winter can see several feet of snow on the rim. Head out to Grand Canyon in the Summer and hike to the bottom near the Colorado River and you will likely see temperatures soaring into the low 120's. In order to stay cool, take breaks along Bright Angel Creek, and just get wet! Your cotton shirt will keep you cool for at least a good 1/2 hour of hiking (nothing stays wet for long in the desert). Since the air is so dry, you will dry off quickly, so little to no chafing. Even if your skin does experience chafing, better that than heat exhaustion, or worse - heat stroke.
So, next time you are planning that trip to the desert during the hotter months of the year, just remember that the climate is much different in the Southwestern United States than most other places in the US. Save some money and bring along your $5 cotton t-shirts on your warm weather hike(s) and forego the $50 Under Armour wicking shirt. You'll save some cash and maybe your life.