Common household soap can do some serious damage to sensitive skin. To retain moisture in your skin, stay away from deodorant soaps or soaps that contain heavy fragrances, antibacterial elements or alcohol [source: AAD]. All of these ingredients strip essential oils from the skin and leaves sensitive skin vulnerable to a host of allergens and irritants.
All soaps are made of a combination of alkali (base) and some kind of oil or fat, but research has shown that soaps with lower alkali content are less irritating to skin [source: Brody]. Some of the least irritating bath soaps aren't actually soaps at all. They're called syndets, a shortened name for synthetic detergents.
Cetaphil is another famously mild "soap" that isn't really soap at all. It's specifically advertised as a "soap-free, non-alkaline" cleanser. Liquid cleansers and moisturizing bars routinely rank as the least irritating "soaps" on the market in dermatological tests [sources: Brody, Lakshmi and Ring].