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Zoe Diana Draelos, M.D., is a consulting professor of dermatology, Duke University School of Medicine, Durham, N.C. She is investigator, Dermatology Consulting Services, High Point, N.C., and a Dermatology Times Editorial Advisor and co-medical editor.
The short answer is "yes," sunscreens are able to penetrate the skin. This fact is proven by the ability to recover sunscreen chemicals in the urine, but the amounts are extremely small.
Q Are sunscreens able to penetrate the skin?
Does this mean that sunscreens are unsafe? No. The benefits of using sunscreens outweigh the risk of systemic absorption of sunscreen filters. Organic filters are more commonly absorbed than the inorganic titanium dioxide and zinc oxide filters.
This is not as great an issue in adults, in whom the ratio is smaller. I think most dermatologists would be surprised at the trace amounts of topical skincare products recovered in the urine.
Q What is horse chestnut, and why is it sold for the treatment of leg telangiectasias?
A Horse chestnut, also known botanically as Aesculus hippocastanum, is a bark rich in many flavonoids. The list includes: aesculin, aesculetin, aescin, fraxin, scopolin, fraxetin, scopoletin, quercitrin, quercetin and leucoanthocyanins.
Flavonoids are potent antioxidants found in most plant material. The bark extract is used in concentrations of 5 percent to 10 percent to alleviate edema in the legs. Reduction in edema is felt to be beneficial in reducing the appearance of leg veins.
The packaging of the product does not indicate that it treats leg veins, as this would be a drug. But appearance improvement can be claimed without problem in a cosmetic. I am not sure if it is the product itself that reduces the edema or the massage required to apply the product.
Q What is quercetin?
A Quercetin is one of the most important flavonoids found in numerous plant materials, from onions to calendula oil. It has a bright yellow color and is used as a dye under the label Natural Yellow 10. It is both a dietary supplement and a topical cosmeceutical additive.
The antioxidant ability of quercetin is due to the presence of numerous phenolic hydroxy groups that can be accessed by free radicals. Quercetin is 20 times more potent than vitamin C and 50 times more potent than vitamin E. The antioxidant ability of vitamin C can be enhanced by the addition of quercetin. Quercetin has been studied for carcinogenicity and mutagenicity, and no evidence was found for these concerns based on rat feeding studies.