Silicones are synthetic polymers with a backbone composed of repeating units of siloxane (elemental silicon and oxygen), combined with other elements, most often carbon and hydrogen. Thus, silicones can also be called polysiloxanes. Often, the terms “silicone” and “silicon” are mistakenly used interchangeably, when they are actually quite different.Silicon is the 14th element on the periodic table and the second most abundant element in the earth’s crust, after oxygen. In contrast, silicones are always synthetically produced.
As a class, silicones improve the feel, appearance, and performance of cosmetic products. These ingredients act as silky moisturizers, conditioners, solvents, and delivery agents for other skin care ingredients. Silicones are able to help with skin redness and irritation due to their low surface tension, which enables them to spread easily across the surface of skin and form a protective covering. This covering consists of both water-binding and water-resistant molecules. The water-binding portion is the highly flexible and mobile siloxane backbone, which binds to moisture in the air and holds it to the skin. The water-repelling methyl groups orient themselves toward the surface, creating a waterproof “umbrella” that prevents trans-epidermal water loss (TEWL). This property makes silicones useful for water-resistant sunscreens.