Icebreaker makes their clothes out of very high quality merino, which is not itchy at all. I =love= my Icebreaker tops (and the one bottom I have for skiing). I wear it on my skin regularly, and I =hate= itchy clothing.

This stuff is perfect: warm when you need it to be, cool when you need it to be, and not itchy at all. And it doesn't smell, which is a godsent for outdoor sports and work ;-)

=Love= it, no synthetic thermal underwear can beat it for comfort or warmth :-)