Silicones are synthetic polymers made up 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.
 
Silicones have wide spaces between each molecule, which form a molecular lattice. Upon application to the skin, this lattice enables silicones to form a film on the surface while still allowing skin to “breathe”. Oxygen, nitrogen, and other nutrients can still pass through the film formed by silicones. However, most silicones do not allow water to pass through, which is an ideal quality for preventing transepidermal water loss (TEWL) – a leading cause of skin dryness and dehydration.
Over 50 percent of all new cosmetics introduced globally in the last 10 years contain at least one silicone. 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.
 
Specifically, polysilicone-11 functions as a film-forming agent. This film 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. Additionally, this backbone allows the water-repelling methyl groups to orient themselves toward the surface, creating a waterproof “umbrella” that prevents transepidermal water loss (TEWL). Furthermore, the smooth, even film that polysilicone-11 forms can help other beneficial ingredients penetrate the skin more easily, as well as prevent contact with potentially irritating ingredients.