According to Sports Doctor Stephen Pribut:
"Blisters, corns, irritations, infections, athlete’s foot – all of these can happen from bad fitting socks made of the incorrect materials. In fact the use of inappropriate socks has even led to what has been called the “toxic sock syndrome”. Pitted keratolysis, as unpleasant as it sounds occurs in feet which have suffered from excessive perspiration, occlusion, and moisture often in the presence of an increased surface pH. And as far as athlete’s foot goes, remember that a “Dark, Warm, Moist Environment is fungous heaven”. Let’s at least get rid of some of that moisture!
The most frequently used fiber which measures up is CoolMax®. Recently Smartwool has been added to the list of acceptable materials. At times polypropylene has been used for making wickable material for socks. The fibers being hydrophobic is not the sole consideration for the choice of an optimal sock. The mechanical structure of the fibers and their being constructed for “channels” to allow moisture to flow through and the compressibility of the material is also important.
Fibers made of materials that swell with moisture tend to hold moisture and lose their shape. The natural fibers seem to swell more than synthetic fibers: Cotton swells 45%, wool swells about 35% while acrylic will only swell about 5%. Cotton is more than 2 times resistant to the flow of moisture. The cotton sock absorbs and retains moisture and reportedly has more than 10 times the moisture retention of CoolMax®. When the cotton sock is wet, it compresses and loses its shock absorbing properties. And the sock can not breathe while the fibers are swollen and clogged with fluid. They are also subject to shrinking during the washing and drying cycle.
Polypropylene will also shrink in the dryer, so allow them to drip dry. CoolMax® socks may be machine washed and dried and are considered shrink resistant. They are also the fastest drying material. While your feet may not be dry when they perspire, the moisture on your foot is moved to the outside of the sock where it can more readily evaporate.
Wicking is a good thing. It helps keep your body and feet cool in hot weather and helps keep you warm in the cold weather. It assists the thermoregulatory processes of your body."