The characteristic features of these diseases usually allow for identification of the specific disease responsible for the patient's problem. These features become less recognizable, however, in patients with long-standing disease and in patients who happen to have two or more eczematous conditions a the same time. In instances where the diagnosis is unclear,it is sometimes helpful to clear the disease completely through the use of systemic steroids and then, when the steriods are stopped, watch for the evolution of typical features if the diseases recurs.

Dyshidrotic eczema is characterized by a history of preceding dyshidrosis. Thus, on questioning, patients will describe the onset of their disease as consisting of pinhead-sized, noninflammatory vesicles situated on the tips or sides of the fingers. Moreover, on examination, some of these minute noninflammatory vesicles can usually be found adjacent to or within the eczematous plaques. Often these vesicles are so closely set they lead to the development of larger, multiloculated bullae. As dyshidrosis becomes increasingly eczematized, there is extension of the vesicular process from the fingers on to the palms, and through the process of autoeczematization, there may also be extension of the eczematous process onto the dorsal surface of the fingers and hands. By the time the whole hand has become involved all evidence of the original, preceding vesicular disease may have disappeared, leaving the patient's description of the original lesions as the only clue to the dyshidrotic nature of the problem.

Atopic dermatitis begins quite differently. There is no historical or visible evidence of a distinct, non inflammatory, vesicular phase. Instead, patients indicate that itching precedes all evidence of skin eruption. The moment scratching begins, however, there is the sudden appearance of a vigorous inflammatory reaction characterized by redness, swelling, weeping, crusting, and excoriation. These initial plaques of atopic dermatitis are found on the dorsal surface of the fingers and hands. Later in the course of the disease, varying degrees of autoeczematization sometimes lead to the development of eczematous lesions on the palms, wrists, and forearms. The itch-scratch cycle as defined is invariably present.