ALLERGIC AND NONALLERGIC ECZEMATOUS DERMATITIS

Abstract

To discuss nonallergic eczematous dermatitis, there must be a clear understanding of allergic eczematous dermatitis, and an understanding of the term eczema itself. The term eczema , which translates as bubbling over, lends itself to confusion and misusage. All too often, the term eczema is used nonspecifically, resulting in confusion for patients and doctors. Although this term is commonly used in other countries, many dermatologists in the United States avoid the term because of its ambiguity but realize the common recognition of the word by the lay public. In general, the unqualified term eczema usually refers to atopic dermatitis. When used in nonatopic settings, eczema is synonymous with dermatitis and requires a qualifying term to be useful (contact dermatitis, stasis dermatitis, or contact eczema, stasis eczema). Throughout this article, dermatitis is used in place of eczema and, with modifiers, refers to all the various eczematous skin eruptions. The term allergic usually refers to an immunologically mediated process in response to an allergen. Allergic contact dermatitis is mediated in part by T-cell activation following exposure to certain antigens contacted by the skin. Urticaria, an allergic disease mediated by IgE antibodies in response to specific antigens, is not considered a dermatitis per se and is not discussed in this article. Atopic dermatitis is frequently considered an allergic dermatitis although the precise immunologic mechanisms in atopic dermatitis are not completely understood. Elevated serum IgE levels plus the coexistence of IgE-mediated diseases seen in atopy (allergic rhinitis and asthma) suggest that atopic dermatitis is triggered by allergic phenomena. This article reviews the pathophysiology, clinical features, and treatment of atopic dermatitis, allergic contact dermatitis, and common dermatitides that have similar presentations but are considered nonallergic (Table 1).