Wool should be washed by hand unless your washing machine has an extremely gentle wool cycle able to wash in cool water. Many older machines wash at 85 degrees Fahrenheit, which is far too hot.  To avoid fulling your finished knitwear, keep two factors in mind. Do not use much soap and then only an approved wool detergent or a mild hair shampoo. Be careful to maintain the same temperature (cool) throughout the wash. When the knitwear is washed and rinsed, it is a good idea to centrifuge it lightly (preferably in a pillowcase or washing bag). Lay your knitwear on a towel and allow it to dry.

Wool knitwear does not require frequent washing. Airing it out in humid weather is often sufficient.