Radical protection by differently composed creams in the UV/VIS and IR spectral ranges

Modern sunscreens are well suited to provide sufficient protection in the UV range because the filter substances absorb or scatter UV radiation. Although up to 50% of radicals are formed in the visible and infrared spectral range during solar radiation protection strategies are not provided in this range. Previous investigations of commercially available products have shown that in addition to physical filters, antioxidants (AO) are necessary to provide protective effects in the infrared range by neutralizing already formed radicals. In this study, the efficacy of filter substances and AO to reduce radical formation in both spectral ranges was investigated after UV/VIS or IR irradiation. Optical properties and radical protection were determined for the investigated creams. It was found that organic UV filters lower radical formation in the UV/VIS range to 35% compared to untreated skin, independent of the presence of AO. Further reduction to 14% was reached by addition of 2% physical filters, whereas physical filters alone were ineffective in the UV/VIS range due to the low concentration. In contrast, this filter type reduced radical formation in the IR range significantly to 65%; similar effects were aroused after application of AO. Sunscreens which contain organic UV filters, physical filters and AO ensure protection in the complete solar spectrum. Free radicals in the skin are not only produced in the UV spectral range, up to 50% are formed in the visible and infrared spectral range. Therefore, protection strategies for these spectral ranges need to be provided. In this study, we could show that both antioxidants and physical filter can reduce radical formation in the IR spectral range and that a combination of physical and organic filters shows best protection in the UV/VIS spectral range. Sunscreens which contain organic UV filters, physical filters and antioxidants ensure protection in the complete solar spectrum.