Cocamidopropyl Betaine

Cocamidopropyl betaine is a surfactant that comes from coconut oil, and it's a common ingredient in many liquid skin cleansers [source: Reitschal]. Surfactants are detergents that allow water to wash away the oil and dirt from your skin by decreasing the surface tension of water and making it easier to wet your face. Surfactants are both lipophilic -- oil loving -- and hydrophilic -- water loving -- which enables them to remove dirt and oil from your skin.

Some surfactants are harsher on skin than others, but cocamidopropyl betaine typically doesn't cause irritation [source: Loden]. In fact, it's often used in cleansers because of its thickening and foaming properties, which help moisturize the skin [source: Medscape]. Cocamidopropyl betaine is even found in many baby soaps and shampoos. However, some people can have allergic reactions to the chemical compound. If using cosmetics that contain cocamidopropyl betaine cause your skin to redden, itch or flake, talk to a dermatologist -- the surfactant can cause contact dermatitis [source: Reitschal].

[source: HowStuffWorks].