I wrote about sheep's wool and water a couple of weeks ago. In short: wool improves with washing. Wash it carefully, but do wash it.
I talk about this a fair bit, in my Blocking class, in my Finishing classes, and whenever given the opportunity.
There's a follow-up question I've heard a number of times recently... I thought it was worth addressing.
(Forgive some lazy sociology and history on my part, please.)
In the Western World, the last few generations have had the luxury of automatic clothes washing and drying machines. They have made a huge change in the lives of so many. And we've enjoyed them so very much that it's changed now only how we do our laundry, but how we think about laundry and fabrics and fibers.
To the point where I think we're not aware that it's possible to clean your clothes without them.
I'm a big fan of air-drying my clothes: it saves power, it saves wear-and-tear on my clothes, and in the winter it humidifies the apartment. I take the items out of the washer, hang them on the rack, leave them overnight. The next day, everything goes for a quick ten or fifteen-minute spin in the dryer to soften it all up. Done.
If it's a heavy item - like, oh, I don't know, a sweater - I might choose to lay it flat on top of a towel on the flat portion of the rack.
But yeah, everything gets air-dried.
More than once, recently, when discussing methods for handwashing sweaters, I've been asked if the pieces will mildew if you don't put them in the clothes dryer.
I was a little puzzled at first, I'll be honest.
But then I realized... the younger knitters I was talking to had likely never hand-washed anything. They'd likely never air-dried anything.
At the risk of going all 'hippy', air-drying is better for your clothes, better for the environment, and better for your wallet.
If you don't have a laundry rack, lie a towel on the floor or bed or mattress. And as long as there's air circulation around the pieces, they will dry very nicely, with no risk of mildew at all.