A shampoo that contains sulfate likely contains its altered compound, sodium laureth sulfate (SLES), which essentially functions as a surfactant (a compound that can surround and remove oil and dirt). SLES can remove impurities such as dirt or oil, but its detergent-like qualities can also remove natural hair oils and cause excessive dryness or flakiness. Compounds with sulfur may also be more irritating to those with sensitive skin. However, the more serious claim that SLES is carcinogenic is incorrect. Research has demonstrated that SLES does not interact with or damage DNA, which is critical for carcinogenic effects. Still, opting for sulfate-free shampoos can help preserve your hair’s natural oils and be gentler on your skin.