Free Radical Threshold Value: A New Universal Body Constant.

Three evolutionary sources create 'primary' reactive oxygen species (ROS) and 'secondary' lipid oxygen species (LOS), forming the human body's 'free radical ground state'. We present evidence for the existence of a universal free radical threshold value (FRTV), defining the borderline between advantageous and adverse effects of free radicals observed above the free radical ground state. Based on standard vitamin D doses, the calculated amount of ∼3.

How a calculated model of sunscreen film geometry can explain in vitro and in vivo SPF variation.

Spectroscopic in vitro assay has recently gained importance for UVA protection, or even for SPF assessment, as manufacturers are increasingly keen to replace in vivo by in vitro tests. These assays are based on transmission UV spectroscopy of a known amount of sunscreen product spread onto an ultraviolet-transparent substrate. In the most recent European publications or methods, the preferred substrate is a roughened PMMA plate.

Investigation of the homogeneity of the distribution of sunscreen formulations on the human skin: characterization and comparison of two different methods.

The efficacy of sun protection, mostly realized by the application of sunscreen formulations, is commonly described by the sun protection factor (SPF). Previous investigations have shown that the efficacy of the sun protection inter alia depends on the homogeneity of the distribution of the topically applied sunscreen formulation on the human skin. Therefore, suitable methods are required to determine the homogeneity of topically applied substances on the skin surface.