Wool, Cotton, Polyester, and the Bajillion Different Fibers for Your Undies

Ever read the fabric composition label for your underwear? It's getting complicated, as more and more mixed fibers are used. 

Cotton is obviously the most common, as we had been cultivating cotton for a very long time, and it can be done relatively cheaply, at least compared to something like wool or silk.  

And of course we can make fiber out of petroleum products, and we generally call that polyester. The problem is polyester tend not to absorb moisture, so it's generally used as one part of a "moisture-wicking" type base layer that makes you not feel wet and sticky as you sweat by moving the moisture from the skin to the absorbent layer above. 

In the recent years, new versions of fabric based on some variation of plant-derived cellulose hit the market, some of them even protected by trademark as they supposedly are better for something else. But generally, they are based on the fiber of a tree that is nowhere close of being endangered and can be harvested easily and its bulk turned into cellulose to be woven into fabric. Beechnut tree got turned into "Modal" fabric, and other fancy trademarked names using other tree species are all over the place, mostly so they can justify their high prices. 

But a perennial favorite, if expensive, is wool. It is somewhat counterintuitive, but wool is soft, absorbent, and anti-odor. Most people tend to associate wool with winter wear. However, wool is hygroscopic, i.e. it absorbs water, it can work as a base layer. Natural wool also contains lanolin, which inhibits bacteria growth, the true source of bad odor. The main problem is cost and stretch, which is why generally you will find a wool blend (mix of wool fiber and some other fiber) plus a few percentage of spandex to give a little bit of stretch, rather than pure wool, to keep the cost down. 

And even then, wool blend undershirts are expensive compared to pure cotton or pure artificial fiber undershirts. Still, if you have extremely limited space (such as a backpacker or single-bag traveller) merino wool blend based clothing may be the edge you need in packing light. But they typically cost $40 USD each, if not more, and that's several times the cost of typical cotton undershirts. 

Oh and they should be hand washed and air hang dried. 

And try out merino wool blend socks. Those don't stink even as your feet sweat.