Histopathological and immunohistopathological features of irritant and allergic contact dermatitis

Abstract

When the clinical diagnosis of allergic and/or irritant contact dermatitis is not clear-cut, skin biopsy is considered a useful tool of differential diagnosis. In contrast, biopsies of patch tests are not recommended, except for scientific purposes. Histopathological features of positive allergic patch test reactions are typical of a spongiotic dermatitis, whereas those of positive irritant patch test reactions are varied (mainly epidermal necrosis), depending on the nature and/or concentration of irritant chemicals and the reactivity of the skin. New immunocytopathological techniques are of no help in distinguishing between irritant and allergic patch test reactions, since there is little evidence of differential cytokine release. © 2011 Springer-Verlag Berlin Heidelberg.