Sodium Laureth Sulfate (SLES) is an anionic surfactant commonly used in personal care products, despite its reputation for being harsh among some consumers. It is an ethoxylated compound, typically containing an average of two ethylene oxide units in its structure. This ethoxylation process enhances its foaming ability and reduces irritation potential compared to Sodium Lauryl Sulfate (SLS), which lacks ethoxylation.
SLES performs better than SLS in terms of foaming and wetting properties, especially in hard water conditions. Increasing the degree of ethoxylation makes SLES even milder. For instance, sodium laureth-3 sulfate is gentler than sodium laureth-2 sulfate, although this comes at the cost of reduced foam generation. It is compatible with anionic, non-ionic, and amphoteric surfactants, but not with cationic ones. Sulfates are typically salt-responsive and can be easily thickened by combining them with the amphoteric surfactant cocamidopropyl betaine (CAPB). SLES/CAPB blends are among the most extensively studied and form the foundation of many cost-effective cleansing formulations.
SLES remains a very cost-effective and highly efficient foaming agent. Milder, eco-friendly alternatives are available, but they can be up to ten times more expensive. The primary concern with SLES lies in the trace amounts of 1,4-dioxane, a potential human carcinogen, that may be present as a byproduct of the manufacturing process. However, these levels are in the parts-per-million (ppm) range.
Despite ongoing concerns, SLES is generally considered safe and remains a staple ingredient in both cleansing and personal care products thanks to its cost-effectiveness, strong performance, and excellent foaming properties. When properly formulated, it is non-irritating to the skin and continues to provide effective cleansing. Due to its excellent performance and low cost, it is commonly used in most personal care products.
