Dry Skin and the Environment

On the other hand, an increase in environmental humidity also induced abnormalities in permeability homeostasis [9] . In this issue of Exogenous Dermatology, environmental factors on dry skin are discussed by fi ve distinguished experts (or their groups) in this fi eld: Wertz (this issue) gives an integrated overview of the epidermal barrier function and their regional variations. His contribution focuses on lipids of the SC and the relationship of SC hydration and barrier function. Furthermore, the pathophysiological aspects of hyperproliferative epidermal conditions with a decreased SC water content, increased transepidermal water loss and an altered skin surface are discussed. Rawlings (this issue) reports about water and SC biomechanics. The state of SC hydration depends on the supplied water from deeper parts of the skin, the evaporation rate at the surface and the water-binding capacity of the SC. The desquamation and proliferation process is highly dependent on both enzyme activity and the integrity of the intercellular lipid matrix. At high humidity, the epidermal synthesis of lipids and natural moisturizing factor is switched off. The reduction in natural moisturizing factor levels together with lipid composition induces changes in the water content in the different layers of the SC. Subsequently this leads to local secretion of proinfl ammatory cytokines that can, either directly or indiIt is well documented that climatic changes infl uence skin conditions, e.g. epidermal structure and functions. A dry environment for example has an impact on epidermal parameters [1] . Improvement of the stratum corneum (SC) homeostasis can ameliorate skin damage induced by barrier disruption in a dry environment [2] . Furthermore, a dry environment directly increases the epidermal level of pro-infl ammatory cytokines [3] . Thus, epidermal homeostasis is very vulnerable when exposed to dry environmental conditions. Histamine H 1 and H 2 receptor antagonists accelerate skin barrier repair and prevent epidermal hyperplasia induced by barrier disruption in a dry environment [4] . Furthermore, a dry environment increases the epidermal mast cell number and histamine content [5] . A recent publication showed the modulation of gene expression induced in human epidermis by environmental stress [6] : the authors could show a general overexpression of MRP8 and MRP14 (both members of the S100 family) as markers for stressed skin being involved in epidermal repair pathways. Loeffl er and Happle [7] reported an increased susceptibility against irritant patch tests during cold climatic conditions during winter and spring. The climatic impact on epidermal functions could be prevented with the application of a moisturizing cream [8] . The daily treatment is effective in improving mild subclinical infl ammation that is induced on the facial skin by the winter environment [8] . Published online: June 30, 2005