Silicones' Benefits in Antiaging Skin Care

By: Michael S. Starch, Dow Corning Corp.

Posted: November 13, 2008

page 4 of 5

A number of different polymers are used to increase the water resistance of sunscreen formulations. Many are acrylate polymers and silicone manufacturers have produced hybrid silicone-acrylate copolymers that offer the benefits of both. Other silicone film-formers such as silicone resins have been shown to increase the water resistance of sunscreens.

Inorganic sunscreens are gaining in popularity because they can offer more effective protection against ultraviolet radiation, but these sunscreen actives also can present formulation challenges. Both titanium dioxide and zinc oxide are fine powders that are difficult to handle in production due to dusting and concerns about inhalation by production workers. The small particle size of the powders helps reduce their white appearance on the skin, but the natural tendency of the particles to agglomerate negates the benefits of small particle size.

For these reasons, inorganic sunscreens are often sold as dispersions in a fluid. The inorganic particles are subjected to high-shear processing during dispersion production, which breaks up the agglomerated particles. Additives in the dispersion are used to prevent re-agglomeration. Cyclomethicone is a popular carrier fluid for inorganic sunscreen dispersions, particularly when the sunscreen particles have a surface treatment to make them more hydrophobic. Silicone additives such as polyether-modified dimethicones are included to prevent re-agglomeration.

Treatments for Aged Skin
Although protection from ultraviolet radiation is the most effective preventive measure for reducing skin aging, consumers with signs of aging want products that can repair the damage and return skin to a more youthful appearance. This is the realm of skin treatments that are designed to reverse the symptoms of aged skin. Such treatments represent a large part of the skin care market and utilize a variety of active ingredients. Some active ingredients have been used for many years, including tocopherol (vitamin E), retinol (vitamin A) and its derivatives, alpha-hydroxy acids (lactic acid, glycolic acid) and ingredients derived from plants. Advances in biochemistry over the past 5-10 years have produced antiaging ingredients designed to stimulate enzymes in the skin that produce structural proteins and other molecules present in younger skin. Many of these biochemical actives are peptides or peptide derivatives.

One property common to many antiaging actives is that they are fragile molecules and can lose their effectiveness via interaction with other ingredients in the formula. This problem has prompted the development of various delivery systems designed to protect the active ingredient in the formulation and make it available when the formulation is applied to the skin.