Typically, 1 to 2 weeks after an acute inflammation, an extremely pruritic, symmetric, scattered, erythematous eruption with macules, papules, and vesicles develops (Fig. 17-1). The eruption involves the forearms, thighs, legs, trunk, face, hands, neck, and feet in descending order of frequency.2,11 During the evolution of the dermatitis, its morphology may change in a manner consistent with the chronicity (i.e., vesicles to scale). Histopathologically, the findings are not pathognomonic: spongiotic epidermal vesicles associated with a superficial, perivascular lymphohistiocytic infiltrate of the dermis, which may contain scattered eosinophils.28 Immunophenotypic studies of skin have revealed that most of the lymphocytes in the epidermis are CD3+ and CD8+ T cells, whereas those in the dermis are primarily CD4+.25 In the majority of individuals with autosensitization,1 deposition of antibody or complement in affected skin is not detected.