Skin barrier function, epidermal proliferation and differentiation in eczema.

Skin permeability barrier function is impaired in eczema, particularly in contact and atopic dermatitis (AD). In contact dermatitis disruption of the barrier by irritants and allergens is the primary event, followed by sensitization, inflammation, increased epidermal proliferation and changes in differentiation. Genetically impaired skin barrier function is already present in non-lesional and more pronounced in lesional skin in AD. Increased epidermal proliferation and disturbed differentiation, including changes in lipid composition, cause impaired barrier function in AD. Defective permeability barrier function enables the enhanced penetration of environmental allergens into the skin and initiates immunological reactions and inflammation. Barrier dysfunction is therefore crucially involved in the pathogenesis of AD. The atopic syndrome represents a genetically impaired skin barrier function as well as impaired nasal, bronchial, and intestinal mucous membranes leading to AD, allergic rhinitis, bronchial asthma or aggravation of AD. Common treatment strategies for eczema include the application of lipid-based creams and ointments, which aim toward the restoration of the defective permeability barrier, thus helping to normalize proliferation and differentiation.