Booties are made with wool/acrylic blend yarns and a leather sole.  They are perfect for use in strollers and babywearing year round.  The leather sole is naturally water resistant, so they can be worn outside by little walkers (just no puddle jumping!).  Like any footwear – using your booties outside will dirty up the soles. 

If you want to give them a wash, mix a solution of warm water and dish soap, dip a soft cloth into it, wring it out and wipe the exterior of the sole. Use a second clean, damp cloth to wipe off the soap. Dry with a towel. Warm, soapy water will also remove water stains and scuffs. 

Piling (or fuzziness) of the yarn is normal and part of natural wear and tear.  It can be removed (carefully!) with scissors by trimming off the little balls, making sure not to cut too close to the surface.