Human body is perpetually subjected to environmental exposures as sun, natural, urban or industrial pollutions and societal exposures. Skin is the main physiological barrier facing to these different stresses; however its response mechanisms are still not well understood. Skin models are thus necessary to understand skin physiology and behavior in normal conditions or under stress. Because of the large natural interindividual variability and of some difficulties in obtaining human skin biopsies, we have been developing and characterizing different skin models such as reconstructed epidermis in vitro, native pigskin and human keratinocyte cells. These models allow us to study the mechanisms involved in ion homeostasis in correlation with structural organization and biological responses. In the present study, we have characterized the pig ear skin model using micro-particle induced x-ray emission (PIXE) analysis with the aim of evaluating the distribution of inorganic ions under normal or stress conditions together with the transepidermal penetration of external agents, such as aluminum oxides. The nuclear microprobe analysis allowed us to validate the culture conditions of the tissue and we have shown an alteration of the inorganic ion patterns after exposure to a chemical compound (sodium dodecyl sulfate) known for its deleterious effects on the barrier function. Finally, we have shown no transepidermal penetration of aluminum oxides after different exposures to cosmetic formulations. Copyright (C) 2009 John Wiley & Sons, Ltd.Read less <