My daughter was born with a skin condition known as seborrhea.
Most commercial soap is actually detergent. If you wash with a detergent bar of soap your natural body oils are removed. This is why when you use a commercial soap you leave the shower or bath feeling dry, your skin is tight, and you feel the need for lotion. Detergent soaps are made from synthetic chemicals produced in a lab, usually from petroleum products. Non-detergent soaps are made from naturally- occurring ingredients such as animal fats, vegetable fats and lye.
Non-detergent soaps like mine leave your natural body oils in place while removing daily soil and odor. Your body produces oils to shield you from invading bacteria. When you wash with a true soap, these oils remain in place to keep your skin healthy and supple.