ECZEMA is a difficult word to define because it has been applied to a heterogeneous group of disorders. From its Greek derivation, eczema means the "result of boiling out or over." Thus, the weeping, vesiculobullous, acute, poison ivy eruption is clearly a type of eczema, but the term is also used to describe a chronic, localized, lichenified plaque of lichen simplex chronicus in which "boiling over" is hardly descriptive. To deal with this dilemma, many dermatologists simply define eczema as "anything that looks like eczema." In other words, "eczema" is a functional term whose meaning, we hope, will become clearer as its clinical manifestations are discussed.
Although a number of classifications have been proposed, none has been generally accepted. Perhaps the simplest and most useful is the following: Contact dermatitis includes (1) allergic and (2) irritant forms. Noncontact dermatitis includes (1) atopic dermatitis and (2) nonatopic dermatitis, eg, lichen