Penetration Properties and Safety Aspects of Topically Applied Products

have the same effect on epidermal barrier function and skin irritation. Their model was able to differentiate bath oil formulations. Evidence was provided for good skin tolerance of bath oils containing St. John’s wort extract. Lademann and Blume-Peytavi and their group (Skin Pharmacol Physiol 2008;21:312–317) were able to demonstrate the changes in hair cross sections during glucocorticosteroid treatment. Significant differences in the hair cross section could be detected during treatment, while the shape of the hairs was not influenced. The authors suggest optical coherence tomography as a suitable, noninvasive and low-cost measuring technique that can be applied for doping control and screening. Monti et al. (Skin Pharmacol Physiol 2008;21:318–325) compared skin permeation and distribution profiles of two sunscreens using reconstructed human skin and hairless rat skin. Different distribution profiles of the tested formulations could be ascribed to the different lipid compositions of reconstructed human skin and rat skin. Since the physicochemical characteristics of reconstructed skin are closer to those of human skin, the authors suggest that reconstructed human skin models could be suitable to replace human skin in ‘in vitro testing’. Otto et al. (Skin Pharmacol Physiol 2008;21:326–334) showed that neither 10% dimethyl isosorbide nor 10% diethylene glycol monomethyl ether significantly enhanced the skin permeation of the various lipophilic active ingredients or the uptake into the skin. They hypothesized that the effect of dimethyl isosorbide and diethylene glycol monomethyl ether on the solubility of the active ingredients in the skin was counteracted by a simultaneous reduction of the thermodynamic activity in the formulation.