Many varieties of synthetic underwear claim to shed perspiration, breathe easily, and provide great comfort. I disagree.
On a recent winter backcountry skiing trip, I finally swore off wearing synthetic underwear due to the horrific body odor generated. I don’t care what the manufacturers say in denial (I have sampled nearly every brand and variety from Patagonia to REI to North Face) — they all smell. All of my skiing companions notice the same with their clothing, so it’s not a personal quirk.
In their place, I have been very pleased to substitute underwear made both by Smartwool and Ibex. The difference in comfort is palpable – wool simply doesn’t hold an odor, and they breathe and dry about the same as the best synthetics. I find wool also feels less clammy when soaked with perspiration. The only downside is a slightly increased cost, but you can cover that by buying only one or two shirts and washing them easily by hand on an extended trip. While I do use wool for underwear and longjohns (although synthetics aren’t too bad for them), you’ll see a dramatic difference in using a wool longjohn shirt because of the decrease in pit odor.
I’ve extended my woolen wear to T-shirts worn under sweaters during urban travel in the winter and find them entirely comfortable and easily washable on the road.