The primary purpose of cleansing is to remove oil, bacteria, sweat, dirt, and desquamated skin cells from the face and body. However, cleansers can react with lipids and proteins on the skin and incite keratinocytes to release cytokines, all of which can irritate or damage the skin’s surface.1,2 Surface-active substances, known as surfactants, work by reducing the surface tension on the skin and emulsifying dirt.3 There are various kinds of surfactants found in cleansers.
ANIONIC (NEGATIVELY CHARGED) SURFACTANTS
Anionic surfactants form generous foam and have the highest cleansing power. Consequently, these compounds are often found as the primary surfactants in cleansers (Table 6-1). “Soap” contains the anionic surfactant alkyl carboxylate. These anionic agents are potent irritants to the skin,4 and have been found to cause harmful swelling of cell membranes.5,6 The well-known anionic agent (a type of alkyl sulfate) sodium lauryl sulfate (SLS), which strips lipids from the skin, is so irritating that it is used in the research setting to impair the skin barrier in order to test “barrier repair products.” Sodium laureth sulfate (or sodium lauryl ether sulfate, also known as SLES) has good cleansing power but is less likely to provoke irritation than SLS.
TABLE 6-1Anionic Agents used in Surfactants |Favorite Table|Download (.pdf) TABLE 6-1 Anionic Agents used in Surfactants
Alkyl acyl isethionates
Alkyl ether sulfates
Alkyl ethoxy sulfates
CATIONIC (POSITIVELY CHARGED) SURFACTANTS
Cationic surfactants have lower detergent properties than anionic surfactants and are very irritating, but are typically used because of their antimicrobial properties. These surfactants often lead to the hand dermatitis seen in frequent hand washers. Cetrimide, chlorhexidine, and benzalkonium chloride are examples of cationic surfactants.
Amphoteric surfactants exhibit changing properties depending on the pH of the solution. Amphoterics are popular because they lather well, exhibit good cleansing power and compatibility with different pHs, display moderate antimicrobial activity, and cause minimal irritation. Examples include cocamidopropyl betaine, cocoamphoacetate, and cocoamphodiacetate.
Nonionic agents have no electric charge. They are expensive and demonstrate poor cleansing characteristics but are believed to cause less irritation than anionic or cationic cleansers. Nonionic agents have been found to disrupt the skin barrier by solubilizing fatty acids and cholesterol.2 Examples of nonionic surfactants include cocoglucoside, lauryl glucoside, decylglucoside, and coconut diethanolamine (cocamide DEA).
Several factors influence the irritancy potential of cleansers including the amount of time left on the skin, rinsability, pH, and the susceptibility of the skin to irritation. (Individuals with a Baumann Skin Type designated as S4 are more susceptible to irritation because their skin barrier is impaired.) ...