[Immunology of allergic contact dermatitis]

Eczema is one of the most common skin diseases in dermatological practice. The broad medical definition of eczema includes any acute but non-infectious inflammatory reaction of the skin. The relative homogeneity of both the clinical and histological manifestations of eczema is in stark contrast to the profound pathogenetic differences of its various forms. The group of contact dermatitis can be divided into two main categories: irritant and allergic. Irritant contact dermatitis is due to a principally non- immunological inflammatory reaction of the skin to various physical or chemical irritants. In sharp contrast, allergic contact dermatitis is an antigen-specific cellular immune response of the skin, which in general requires prior antigen-recognition and priming of immune cells. A comprehensive understanding of the complex interactions between immune cells, inflammatory mediators and adhesion molecules in the underlying pathogenesis of allergic contact dermatitis is key for a better functional understanding and the development of new therapeutic strategies.