When you are buying wool be sure to look for Merino Wool. It is softer, less scratchy, better at keeping a body regulated (both warm and cool) andbetter at wicking moisture than regular rag wool. Filson uses it exclusively.Most of the better high end wool clothing is Merino from other manufacturers as well. I have had great success with both Merino and synthetic underwear and layering pieces. I have had better luck with synthetics during more vigorous activities and tend to lean to the wools when the activity isn't as vigorous. I think it boiles down to personal preference and expected use.