Snapshot A 25-year-old man presents with an itchy rash on his chest wall. He denies any exposures to insects and denies any previous allergies. He recently had an upper respiratory infection. Physical exam shows blanching, raised, edematous annular lesions that are well-circumscribed. Some lesions are coalesced. This is his first episode of this itchy rash. He denies any other symptoms. Introduction Pruritic inflammation of the skin commonly known as “hives” Characterized by superficial, localized edema and erythema Epidemiology login to view 1 more bullet Pathogenesis login to view 5 more bullets Triggers of acute urticarial (< 6 weeks) login to view 11 more bullets Chronic urticarial is usually idiopathic (> 6 weeks) Etiology identified in 40-60% of acute cases and 10-20% in chronic cases Presentation Symptoms login to view 4 more bullets Physical exam login to view 5 more bullets Evaluation Labs or biopsy not indicated for acute urticarial unless diagnosis is unclear ↑ IgE For chronic or recurrent urticarial login to view 1 more bullet Histology of lesion login to view 2 more bullets Differential Diagnosis Hereditary angioedema Contact dermatitis Multiple insect bites Erythema multiforme Treatment If known, discontinue offending agent If concern for airway compromise login to view 1 more bullet Anti-histamines login to view 1 more bullet Prognosis, Prevention, and Complications Prognosis login to view 1 more bullet Prevention login to view 2 more bullets Complications login to view 1 more bullet