All wool can be washed. Many wool yarns are treated so they can easily be machine washed, and many other wool yarns can be gently washed in the machine as well.
I am a lunch supervisor in a kindergarten division (90+ kids) and I've been knitting (and sewing) wool mittens to have on hand for "emergencies". I have found that once kids try wool mittens (getting them to trust them, over the expensive store bought gloves from home, is the big hurdle), they love them. The keys are to knit them tightly and wash before use so that the spinning oils are removed and the yarn blooms. You can even do a lanolin soak for extra waterproofness.
But the joy on a kids' face when they come in from lunch and hand me back soggy mittens and say "My hands are still warm"? Priceless!
Yarn In: 8023grYarn Out: 23gr + 8729gr =8752gr
Balance: 729gr more USED than bought
Costs: $351.86 /366 days = $0.96/day