Pediatric emergency medicine trisk 1850 1850

causing degranulation of mast cells (e.g., radiocontrast material) Episodes of urticaria lasting less than weeks are termed transient or acute The most common causes of urticaria are infection, insect bites, drugs, and foods Chronic urticaria is defined as that which lasts for more than weeks No cause is found in 90% of children These cases include the physical urticarias or urticarial vasculitis The lesion itself follows vasodilation and leakage of fluid and red blood cells from involved vessels The vascular damage can be caused by mediators such as histamine complement and immune complexes IgE can attach to and cause degranulation of mast cells in sensitized individuals, with resulting histamine release Clinical Manifestations The typical urticarial lesions are familiar to all physicians They can be localized or generalized (involving the entire body) At times, the lesions are giant with serpiginous borders Individual wheals rarely last more than 12 to 24 hours Most commonly, the lesions appear in one area for 20 minutes to hours, disappear, and then reappear in another location The total duration of an episode is usually 24 to 48 hours; however, the course can last to weeks In young children, urticaria may have an annular or polycyclic (coalescent annular) or arcuate (partially annular) appearance and may be associated with edema of the hands or feet Because this is frequently confused with EM (which manifest with more fixed, targetoid lesions), this annular urticarial hypersensitivity has sometimes been referred to as urticaria multiforme Management Acute relief can be accomplished by oral diphenhydramine mg/kg (max 50 mg) Oral antihistamines are useful for maintenance therapy for transient urticaria H1 antihistamines for to weeks are usually effective for controlling urticaria Many recommend combinations of H1 and H2 antihistamines, but there is currently insufficient evidence to support this as a routine practice Shorter-acting agents like hydroxyzine can be used for breakthrough Suggested Readings and Key References General Eichenfield LF, Esterly NB, Frieden IJ Textbook of Neonatal Dermatology Philadelphia, PA: Elsevier Health Sciences, 2014 Goldsmith L, Papier A VisualDx: Essential Pediatric Dermatology Visual Dx: The Modern Library of Visual Medicine Philadelphia, PA: Lippincott Williams