People have been using soap in various forms for thousands of years, so it might seem like a no-brainer to just go with the flow and keep doing things the same way. But non-soaps have their advantages over soaps.
A main advantage of non-soap bars is that they are formulated not to leave soap scum in hard water. In fact, one of the reasons non-soap products were developed was that soap doesn't do so well in hard water. Water is considered to be hard when it has minerals such as calcium and magnesium in it. The ingredients in soap react to those calcium and magnesium ions, and, as a result, they can leave behind a film on your skin and on your tub. With non-soap bars, you're less likely to wind up with soap scum from washing or bathing in hard water [sources: The Soap and Detergent Association, Oakley].
Non-soap bars are often gentler on the skin, too. They ingredients are milder and generally don't strip away excess oil, so you shouldn't have to worry as much about dry or irritated skin. Also, many health experts believe that the pH level of non-soap bars should be more compatible your skin's natural level. On the acidity-measuring scale of 0 to 14, skin usually has a pH of about 4.5 to 6.5, whereas soap tends to have a higher pH at about 9 or 10. In contrast, non-soap cleansers can be designed to have a specific pH that is closer to that of your skin. Some people say the difference in pH can have a negative impact on your skin, but the issue is still being researched, so the jury's still out on this one [source: Draelos].
Both soaps and non-soap cleansers will get you clean, so picking the perfect bar has more to do with personal preference than anything else. For more information on choosing the right soap for you, explore some of the links and articles on the next page.