The distribution and appearance of the dermatitis and a detailed exposure history are the most useful diagnostic tools. Involvement of the lower legs and distal arms suggests exposure to plants of the Rhus species (poison ivy or poison oak), especially when linear configurations of lesions are present. Dermatitis of the ears (earrings), wrist (bracelet or watch), or periumbilical region (belt buckle or pant buttons) suggests a metal allergy to nickel. Distribution on the dorsal surfaces of the feet indicates a shoe allergy, usually to dyes, rubber, or leather. Topical antibiotics (neomycin) and fragrances (soaps, perfumes, cosmetics) are frequent causes of allergic contact dermatitis.
Diaper rashes caused by Candida are quite common. Irritant contact dermatitis primarily affects the prominent, exposed surfaces, whereas Candida primarily affects intertriginous areas. The two are frequently present simultaneously, as secondary Candida infection may complicate irritant dermatitis.
Psoriasis, seborrheic dermatitis, and Langerhans cell histiocytosis can present with an erythematous rash in the diaperarea. Referral to a dermatologist should be considered for anychild with severe rash or with diaper rash that does not respondto conventional therapy.
Topical corticosteroids are effective in treatment of allergic and irritant contact dermatitis. High-potency corticosteroids, and even short courses of oral corticosteroids, may be necessary for severe reactions of allergic contact dermatitis. Oral antihistamines may be required to control itching.
Treatment of candidal diaper dermatitis consists of topical nystatin or topical azole antifungals. Low-potency topical corticosteroids are frequently used in addition to topical anti-fungal therapy to treat the irritant component of the diaper dermatitis when present concomitantly.
In addition to superinfection of diaper dermatitis by C. albicans, bacterial superinfection may complicate any form of contactdermatitis. This is especially common if the skin barrier is nolonger intact because of blistering or scratching.
Every effort should be made to identify the trigger of allergic or irritant contact dermatitis. With allergic contact dermatitis, reexposure often leads to increasingly severe reactions.
Seborrheic dermatitis is a common, chronic inflammatory disease that has different clinical presentations at different ages. Seborrheic dermatitis classically presents in infants as cradle cap or dermatitis in the intertriginous areas of the axillae, groin, antecubital and popliteal fossae, and umbilicus. It is seen in adolescents as dandruff. The pathogenesis of seborrheic dermatitis is unclear, but it is theorized that there is an abnormal inflammatory response to commensal Malassezia species in sebum-rich areas. Areas prone to seborrheic dermatitis include the scalp, eyebrows, eyelids, nasolabial folds, external auditory canals, and posterior auricular folds.
Seborrheic dermatitis in infants begins during the first month and persists during the first year of life. It is also called cradle cap because of the thick, greasy and waxy, yellow-white scaling and crusting of the scalp (Fig. 192-1). It is usually prominent on the vertex of the scalp, but it may be diffuse. Greasy, scaly, erythematous, nonpruritic patches and plaques may extend to the face and posterior auricular folds, sometimes involving the entire body. Diaper and intertriginous areas can have sharply demarcated, shiny, erythematous patches with yellow, greasy, or waxy-appearing scale. Hypopigmentation may persist after the inflammation has faded. The eruption is usually asymptomatic, which helps differentiate it from infantile atopic dermatitis, which is pruritic.