That's another reason to swatch and wash your swatch before you start a project! I bought a hemp blend and wasn't sure that I would want it next to my skin, but after I washed the swatch it was wonderfully soft.
Wool varies a lot...I was hoping that the Bartlett fisherman's wool that I bought for a sweater would soften up, but it didn't. I still used it for my cardigan, but it's on the itchy side, even with a shirt between the sweater and my skin. :-x