Diagnosis	Distinguishing features
Atopic dermatitis	Chronic or relapsing pruritic lesions and abnormally dry skin; flexural lichenification is common in adults; facial and extensor involvement is common in children
Candidiasis	Erythematous papules or red, moist plaques; usually confined to mucous membranes or intertriginous areas
Contact dermatitis	Pruritic areas with weeping on sensitized skin that comes in contact with haptens (e.g., poison ivy)
Dermatophytosis	Lesions may be scaly and red with slightly raised “active border” or classic ringworm; or may be vesicular, especially on feet
Discoid lupus erythematosus	Well-defined plaques with adherent scale that penetrates into hair follicles; peeled scales have “carpet tack” appearance
Ecthyma	Crusted lesions that cover an ulceration rather than an erosion; may persist for weeks and may heal with scarring as the infection extends to the dermis
Herpes simplex virus	Vesicles on an erythematous base that rupture to become erosions covered by crusts, usually on the lips and skin
Insect bites	Papules usually seen at site of bite, which may be painful; may have associated urticaria
Pemphigus foliaceus	Serum and crusts with occasional vesicles, usually starting on the face in a butterfly distribution or on the scalp, chest, and upper back as areas of erythema, scaling, crusting, or occasional bullae
Scabies	Lesions consist of burrows and small, discrete vesicles, often in finger webs; nocturnal pruritus is characteristic
Sweet's syndrome	Abrupt onset of tender or painful plaques or nodules with occasional vesicles or pustules
Varicella	Thin-walled vesicles on an erythematous base that start on trunk and spread to face and extremities; vesicles break and crusts form; lesions of different stages are present at the same time in a given body area as new crops develop