Ultrastructure of irritant and allergic contact dermatitis

Abstract

The ultrastructural changes seen in acute contact dermatitis vary according to the chemical nature and concentration of the substance applied to the skin, the intensity of the response and the time of biopsy. In general, irritants have a greater impact on the stratum corneum than allergens, and produce a wider variety of morphological changes in the viable layers of the epidermis, a reflection of the heterogeneity in their mechanisms of action. Allergic contact dermatitis reactions are generally more uniform, the predominant ultrastructural changes being spongiosis, vesiculation and exocytosis. Epidermal Langerhans cells within both allergic and irritant patch test reactions show ultrastructural evidence of activation and degeneration, and are frequently seen in apposition to lymphocytes. Oedema and capillary dilation are the most commonly described features within the dermis of allergic and irritant patch test reactions. Our knowledge of the ultrastructure of chronic contact dermatitis remains limited. © 2011 Springer-Verlag Berlin Heidelberg.