Jay Zimmerman, Board-certified Family Physician; and OASC Leader and Member since May 2006

Dear Dr. Jay,

I have been on several hikes with the club, and am curious about why hikers shouldn't wear cotton. Can you explain why leaders prefer their hikers to wear a material other than cotton while hiking? I love my cotton t-shirts; they are so comfortable! And I was asked not to wear jeans again while hiking...why?? Can you give specific examples of clothing that is cotton, and clothing that is not? And are there times when wearing cotton is ok?

Thank you!

~Luv My T-Shirt & Jeans!
 

Dear Luv My T-Shirt & Jeans,

Who doesn't love T-shirt & jeans?! They certainly feel great and are a favorite of mine around home & downtown, but they have limited use when hiking and backpacking.

You see, jeans, canvas and most T's are all made of cotton. When cotton gets wet, it gets heavier & more uncomfortable. Unfortunately, cotton usually takes a long time to dry. It will then cling to your body, making you lose heat. For this reason, it'd be OK to use when the temperature is high & the humidity in the air is really low- perfect for the hot desert. Since most people sweat when they hike or backpack, they generate moisture in many areas. You need your clothing to let your sweat and some body heat escape; otherwise you get too hot too quickly and are no longer comfortable. On a cold day, letting some sweat escape can also reduce your heat loss.

When wearing cotton on a cold day, once you stop your body can cool too quickly. This is because cotton increases two types of heat loss: the evaporative and conductive heat loss. Even if you don't stop, your body can cool off too much! OASC leaders are worried about hypothermia, a serious threat to a person and a group. You can start shivering and your extremities get cold. Later stages can make people act irrationally- go in the wrong direction, stop moving toward the right goal. As crazy as it sounds, some people with extreme hypothermia will even strip off their warm clothing!

I recommend hiking with wicking clothing like polypro (polypropelene), or other synthetics (like fleece). Two other natural choices are lightweight wool and silk. In the cold, make sure everything is in layers so if you get too hot you can remove a layer or add when you stop. I also recommend starting with fewer layers so that you will be a little cool when you first start hiking- that way when you start to warm up, you won't need to de-layer!

Dr J

Ask Dr. Jay is not intended to address specific questions concerning individual cases, so please keep your question general in nature. Questions and answers here are not a substitute for medical advice from your Physician. Please contact your doctor if you need medical advice or treatment, or have any questions regarding a medical condition.