Sodium hydroxide, commonly known as lye, is a strong alkali produced by reacting sodium metal with water. It is widely used in various industrial processes, including soapmaking, paper production, and textile manufacturing. In cosmetics, sodium hydroxide acts as a pH adjuster, emulsifier, and thickening agent. It is often found in soaps, detergents, and hair relaxers. While sodium hydroxide is considered safe when used in low concentrations and under proper conditions, prolonged or excessive exposure can cause skin and eye irritation, burns, and other health issues.