CHAPTER 65 ■ RASH: ATOPIC/CONTACT DERMATITIS AND PHOTOSENSITIVITY JOY WAN DERMATITIS Dermatitis is the general term used to describe an itchy, eczematous rash In its acute form dermatitis is characterized by erythema, edema, exudation, scattered papules or vesicles, scaling, and crusting Chronic dermatitis is characterized by lichenification (accentuated skin markings), hyperpigmentation, hypopigmentation, and excoriations Diagnosis of the underlying cause of the dermatitis relies on patient history and physical examination findings; histology is typically nonspecific This chapter highlights common causes of dermatitis in children, including atopic dermatitis, nummular eczema, asteatotic eczema, dyshidrotic eczema, lichen simplex chronicus, and contact dermatitis Atopic Dermatitis Atopic dermatitis is the most common cause of dermatitis in children ( Table 65.1 ), occurring in 10% to 20% of children It is a chronic and relapsing condition characterized by pruritic eczematous papules, patches, and plaques There is often a personal or family history of allergic rhinitis, hay fever, or asthma Many patients have the onset of symptoms before months of age, with most developing symptoms by years of age Heat, stress, sweating, infection, and exposure to environmental (e.g., pet dander, pollen) and contact allergens (e.g., fragrances, soaps) may precipitate flares The diagnosis is mainly based on typical history and physical examination findings, and the American Academy of Dermatology has developed criteria to summarize these features ( Table 65.2 ) The broad differential diagnosis requires the exclusion of other skin conditions that present in a similar fashion, including seborrheic dermatitis, scabies, psoriasis, nutritional deficiencies (i.e., zinc), immune deficiencies, and cutaneous lymphoma Importantly, while superficial bacterial infections,