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Quenching Excited States—What does this mean? Perhaps the sigh of relief you exhale when your anticipated Cosmetics & Toiletries magazine arrives. Or, in the spirit of Valentine’s Day this month, that gasp of excitement and kiss emitted when your true love finally presents a long-awaited and desired diamond ring. In any case, an excited state suggests a buildup that needs some form of release before it causes any damage. A similar dynamic exists within sunscreen systems.
Now that this explosive cover has captured your attention, here’s the bottom line: UV radiation wreaks havoc on skin. Scientists have proven it, formulators are addressing it, and consumers are finally starting to believe it. This is nothing new to you, dear reader, but what is new is the approach chemists are taking to provide sunburn protection.
In studying the reactions of sunscreens to UV exposure, chemists and formulators recognize that stability is an issue. Sunscreens are designed to absorb energy so that the skin does not, or at least so that it absorbs less of it. In doing so, materials in the formulation are excited with this added energy. So where does the extra energy go?
Craig Bonda tells us in his article, in which he provides a visual depiction to describe the pathways energy can take; for example, an electron energized by UV causes an electromagnetic disturbance in the space around it that may spawn yet another photon. In addition to drawing a “map” of energy pathways, Bonda discusses a new means of preserving photostability: by quenching the UV filter’s singlet excited state.
This approach covers protection of all skin, but UV radiation is especially harmful to patients dealing with acne-prone skin. In their article, Pierfrancesco Morganti and co-authors discuss how well-known anti-acne pharmaceutical products often are based on benzoyl peroxide or retinoic acid and cannot be used on sun-exposed skin because of their sun-sensitization properties. Thus, a sun care solution specifically designed for acne-prone skin is presented.