The chemistry involved in producing a moisturizing body wash is different from producing either an individual cleanser or an individual moisturizer -- the two skin-care products must be fused together by creating an emulsion, which is a mixture of water and oil [source: Case].
Oil and water don't naturally mix, so a chemical called a surfactant is added to the mix. Surfactants bind to both water and oil, thereby linking the two ingredients -- that is, until you bathe [source: Case]. When you lather up, the moisturizing oils break down and are deposited into the skin [source: Draelos]. So, with one emulsion you're able to cleanse the skin with both water and cleansing ingredients -- while moisturizing the skin with oil-based or oil-soluble moisturizers.
A typical moisturizing cream is 50 percent water and 50 percent oil, but a body wash needs to retain its liquid cleansing properties. [source: American Academy of Dermatology]. So, in the case of moisturizing body washes, the ratio must be changed to incorporate more water than oil. Your skin needs oil to be properly moisturized, but slathering on mineral oil is a messy process. An emulsion, which is half water, goes on cleanly, and the water evaporates, leaving behind a layer of oil.
Keep reading to learn what other ingredients may be added to your moisturizing body wash.