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Formula Anatomy Deciphered—Sun Damage Prevention and Repair
By: Eric S. Abruyn, TPC2 Advisors Ltd., Inc.
Posted: March 2, 2011, from the March 2011 issue of Cosmetics & Toiletries.
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Sunscreen components: Key to sun damage prevention are sunscreen actives that are generally classified as organic or inorganic UV filters. Organic UV filters strongly absorb radiation at specific wavelengths and are transparent to visible light.4, 5 There are many efficacious UV filters that can be incorporated into most sunscreen formulations. Popular UVB filters include homosalate, octisalate and octocrylene, while avobenzone is a popular UVA filter; titanium dioxide, zinc oxide and oxybenzone can provide both broad-spectrum UVB and UVA protection.
Additionally, a number of effective UV sunscreen actives are currently awaiting approval by the US Food and Drug Administration (FDA), such as drometrizole trisiloxane, octyl triazone, bemotrizinol and diethylamino hydroxybenzoyl hexyl benzoate. Of course, a single sunscreen active is not sufficient to cover the full spectrum of UV radiation, which is necessary to protect the skin.
Sunscreen and sun-exposed treatment formulas come in many forms but two-phase emulsions are the most popular delivery system. These emulsions can be classified as w/o or o/w, both having distinct merits such as versatility of aesthetics or performance efficacy of sunscreening agents. W/O emulsions deliver better water resistance and higher effective-yielding SPF. Conversely, o/w emulsions are more widely used due to their lower inherent cost (higher water content). Lately, more formulators are creating aerosol sunscreen sprays because they allow for quick, clean and easy application. No matter what type of formulation and applicator is used, however, the concern for adequate and effective application by the consumer remains.
Sun damage repair: Sun damage repair can be imparted via different mechanisms and in varying degrees. Botanicals are one example of functional ingredients that repair UV damage through antioxidant effects and the sequestering of ROS formation. Typical botanical extracts chosen are pomegranate, grape and berries such as açai. While these extracts possess antioxidant properties to neutralize ROS formation on UV-exposed skin, they would need to be used in active levels greater than 0.1% to provide their benefits topically.
Besides botanicals, peptides such as copper tripeptide-1 and palmitoyl penta- peptide-3 have been used to initiate skin repair mechanisms such as: stimulating collagen; promoting synthesis of elastin, proteoglycans, glycosaminoglycans and other components of the skin matrix; stimulating capillary formation and the ability to regulate the growth rate and migration of different types of cells; imparting anti-inflammatory action; and enhancing skin defense mechanisms such as promoting the release of oxidation-promoting iron into the tissues as well as detoxification. Other ingredients reported to provide repair from UV radiation damage are vitamin C and retinoids (e.g., retinol) in addition to both of their analogs.