Because wool is a natural fibre any discomfort is more apt to be from it being next-to-skin rather than anything else. During my times in brutally hot locales - well over 80 degrees - I always wore wool socks with my boots to allow the fibre to do its job of insulation (it works both ways) and to wick moisture (extend the sock top over the boot top). With my skin a bit sensitive to the wool contacting directly, I wore a very thin 'liner' sock. Months at a time and never a problem. I would think then that if wool itch from the kilt is a concern, a nice loose cotton undergarment would be sufficient.