New Approach to Develop Optimized Sunscreens that Enable Cutaneous Vitamin D Formation with Minimal Erythema Risk.

Sunscreens protect the skin against erythemal radiation (Eer). But at the same time they reduce the effective radiation dose (EVD) responsible for the formation of previtamin D in the skin. The paper describes a calculation method for optimizing the ratio EVD/Eer behind sunscreens e.g. with SPF 5, 15 and 30 respectively. Taking into account that a majority of people in industrialized countries suffer from a shortage in vitamin D even in summer time, the ratio Evd/Eer is a new and important criterion for the quality of sunscreens. Furthermore the exposure time tvd needed per day for forming the equivalent of the recommended amount of 2000 IU of vitamin D per day for skin type 2 is estimated when sunscreens with different filter compositions are used. In vitro experiments show a significant increase of the conversion of 7-dehydrocholesterol (7-DHC) to previtamin D when exposed to artificial solar radiation behind an experimental sunscreen optimized for previtamin D production compared to a commercial sunscreen having the same SPF

The Missing Link - Light-Induced (280-1,600 nm) Free Radical Formation in Human Skin

The recent European recommendation on the efficacy of sunscreen products requests now a minimum ratio of UVA/UVB protection. However, the visible and the infrared (IR) parts of the sun spectrum have received little attention concerning their possible contribution to skin damage. A common biophysical answer for the different wavelengths of the sun spectrum can be found in the creation of excess free radicals - mainly reactive oxygen species (ROS). Thanks to electron spin resonance spectroscopy applied to skin biopsies, we determined for the first time the free radical action spectrum covering UV and visible light (280 - 700 nm). Convolution of the action spectrum with sunlight spectral irradiance showed that 50\% of the total skin oxidative burden was generated by visible light. Creation of ROS by visible light was experimentally confirmed by varying the illuminance of a spotlight. We also evidenced the creation of excess free radicals by near-IR radiation. In that case, free radical generation does not depend exclusively on the dose, but also on the skin temperature increase initiated by near-IR light. Some phenomena which are still unclear, such as the question about the deleterious or beneficial role of sunlight, are reviewed, implying the research on new protection strategies for the prevention of skin cancer. Copyright (C) 2008 S. Karger AG, Base

Action spectra for erythema and for previtamin D formation in human skin and standard solar spectral irradiance at the surface of the earth.

<p>Action spectra for erythema and for previtamin D formation in human skin and standard solar spectral irradiance at the surface of the earth.</p

<i>In vitro</i> conversion of 7-DHC to previtamin D after irradiation with simulated UV solar radiation.

<p>Mean values +/- SE.</p

Calculated SPF, E_VD/E_er and AF_VD of both a commercially available sunscreen (Neutrogena) and an experimental sunscreen named Solar D which was optimized to a low attenuation factor AF_VD.

<p>Calculated SPF, E_VD/E_er and AF_VD of both a commercially available sunscreen (Neutrogena) and an experimental sunscreen named Solar D which was optimized to a low attenuation factor AF_VD.</p

UV filter compositions for SPF 15 with different levels of E_vd/E_er ratio and UV-A protection.

<p>UV filter compositions for SPF 15 with different levels of E_vd/E_er ratio and UV-A protection.</p

UV filter compositions for SPF 30 with different levels of E_vd/E_er ratio and UV-A protection.

<p>UV filter compositions for SPF 30 with different levels of E_vd/E_er ratio and UV-A protection.</p

Spectra of simulated UV transmittances of four SPF 15 sunscreens (compositions in Table 2) with weak, intermediate, strong UV-A and previtamin D optimized protective properties; small graph: transmittance scale enlarged in the spectral range from 290 to 330 nm.

<p>Spectra of simulated UV transmittances of four SPF 15 sunscreens (compositions in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0145509#pone.0145509.t002" target="_blank">Table 2</a>) with weak, intermediate, strong UV-A and previtamin D optimized protective properties; small graph: transmittance scale enlarged in the spectral range from 290 to 330 nm.</p

Effective spectral irradiances for both erythema and previtamin D formation when using standard spectrum of solar radiation COLIPA without sunscreen.

<p>Effective spectral irradiances for both erythema and previtamin D formation when using standard spectrum of solar radiation COLIPA without sunscreen.</p