I just scrub the with a brush and cut out any part that I have doubts about. Oil the skins and bake in a hot oven. My mother told me...not that I believe it... that "you have to eat a tablespoon of dirt a day to stay healthy." Her mother told her. They probably had limited water in the "old country." But, she always washed her potatoes first! I do the same thing for sweet potato. I always eat the skin on both kinds.