The tapes utilized removed a similar amount of SC. The tapes have a different propensity to cause barrier disruption. Some individuals do not demonstrate increased TEWL despite an equivalent mass of SC being removed compared to those who do show a response.
In this randomized, double-blind human study, the short-term photoprotective effects of different antioxidants and their combinations were evaluated in vivo. Vitamin C (ascorbic acid), vitamin E (alpha-tocopherol) and melatonin (N-acetyl-5-methoxytryptamine) were topically applied, alone or in combination, 30 min before ultraviolet-irradiation of the skin. The erythemal reaction was evaluated visually and non-invasively using different bioengineering methods (skin colour and skin blood flow). The results showed a modest protective effect of the vitamins when applied alone and a dose-dependent photoprotective effect of melatonin. Topical application of combinations of both vitamins, or of melatonin with vitamins, enhanced the photoprotective response. Better protection was obtained by using the combination of melatonin with both vitamins. The role of reactive oxygen species and oxygen-derived free radicals, as well as potential sunscreening properties of the employed antioxidants, are discussed in view of possible mechanisms to explain this elevated photoprotective effect.
Tape stripping results are influenced dramatically by all investigated parameters. A dynamic SC stress test to investigate SC cohesion more closely is proposed based on the present observations.
Human studies have convincingly demonstrated pronounced photoprotective effects of 'natural' and synthetic antioxidants when applied topically before UVR exposure. Particularly with respect to UVB-induced skin damage such as erythema formation, the photoprotective effects of antioxidants are significant when applied in distinct mixtures in appropriate vehicles. Topical application of such combinations may result in a sustained antioxidant capacity of the skin, possibly due to antioxidant synergisms. And, since UVA-induced skin alterations are believed to be largely determined by oxidative processes [26], topical administration of antioxidants might be particularly promising [27, 28]. In fact, topical application of antioxidants or antioxidant mixtures resulted in a remarkable increase in the minimal dose to induce immediate pigment darkening after UVA exposure [18, 23] and diminished the severity of UVA-induced photodermatoses [22] in humans. In conclusion, regular application of skin care products containing antioxidants may be of the utmost benefit in efficiently preparing our skin against exogenous oxidative stressors occurring during daily life. Furthermore, sunscreening agents may also benefit from combination with antioxidants resulting in increased safety and efficacy of such photoprotective products [11, 29].
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