Although there are several different skin types, the basic chemistry of body wash is usually the same. Most skin cleansing products are generally made up of two parts: a lipophilic part, which is fat-soluble, and a hydrophilic part, which is water-soluble. Dirt itself is lipophilic, which means that it won't dissolve in water. Simply rinsing yourself with water after you've got some dirt on yourself won't get you clean. Only something with a fatty product will dissolve the dirt and lift it off your skin.
This combination of lipophilic and hydrophilic ingredients is called a surfactant. A surfactant cleans your skin because the lipophilic part dissolves the dirt on your skin, while the hydrophilic part washes it away. Body washes typically contain mineral oil or petroleum derivatives as their lipophilic part and water as the hydrophilic part. Skin cleansers also may contain several other types of ingredients. Emulsifiers such as diethanolamine (DEA), for instance, keep the chemicals in cleansers from separating into different layers. Biocides, also commonly known as antiseptics, reduce bacteria count on the skin and reduce body odor. Preservatives, meanwhile, keep products on the shelves and in your bathroom cabinet for longer [source: DermNetNZ].
Some liquid skin cleansers actually don't include fatty acids. These are called syndets, which is short for synthetically produced detergent [source: DermNetNZ]. Instead of fats, syndets are made with petrochemicals, which are derived from petroleum, or oleochemicals, which are derived from fats and oils. These can stand in for the lipophilic part of surfactants. Some of the benefits of using syndets over regular soap are that you get less soap scum and bacteria. They're also better for sensitive, dry skin, and for treating acne.
See the next page to find out which types of body wash are right for which skin types -- and which type may be right for you.