The same thing just happened to me when I bought a pair of merino wool shirts (70% merino / 30% acryl). The end of my nips were red raw after a few heavy days cycling. I was going to send them back but they are so light and easy to wash I am going to put little plasters over my nips while I tour. I never got this issue with wool tops but they are just too heavy and make me sweat more.