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Topical application of low-dose green tea extract may help protect against UV damage, without the common side effects. A large body of scientific literature illustrates the protective quality of green tea catechins and polyphenols. However, these studies often investigate the protection provided by high concentration extracts, which have a green brown color and can stain, making them impractical as cosmetic ingredients.
Low concentrations may be effective
Recent research from scientists in Switzerland has looked at the effects of applying low concentrations of green tea extracts over a sustained period of time. According to the study, led by Dr. Christian D. Mnich from the University Hospital of Zurich, topical application of the green tea extract at 0.4% during a five-week period exhibited significant photochemoprotective effects.
During the study period 18 subjects applied the green tea-containing extract--commercially available as OM24 from Switzerland-based company Omnimedica--and a placebo to the skin of the buttocks, chosen as it is protected from UV rays. Subjects applied the lotions three times a day for 34 days, and participants were exposed to UVB rays between two and three hours after application.
According to the researchers there was no significant difference in erythema (skin reddening) between the skin treated with the placebo and the treatment. However, the scientists explained that UV-induced erythema is a limited parameter to quantify damage as it does not always link to p53 expression, a tumour suppressor protein that is induced in cells by UV radiation). In contrast, treatment with the green tea extract reduced the number of UV-induced p53 positive keratinocytes by 31.9% on day six and by 36.3% on day 34.