Urticaria commonly presents with intensely pruritic wheals, sometimes with edema of the subcutaneous or interstitial tissue. It has a lifetime prevalence of about 20%. Although often self-limited and benign, it can cause significant discomfort, continue for months to years, and uncommonly represent a serious systemic disease or life-threatening allergic reaction. Urticaria is caused by immunoglobulin E- and non-immunoglobulin E-mediated release of histamine and other inflammatory mediators from mast cells and basophils. Diagnosis is made clinically; anaphylaxis must be ruled out. Chronic urticaria is idiopathic in 80% to 90% of cases. Only a limited nonspecific laboratory workup should be considered unless elements of the history or physical examination suggest specific underlying conditions. The mainstay of treatment is avoidance of triggers, if identified. The first-line pharmacotherapy is second-generation H1 antihistamines, which can be titrated to greater than standard doses. First-generation H1 antihistamines, H2 antihistamines, leukotriene receptor antagonists, high-potency antihistamines, and brief corticosteroid bursts may be used as adjunctive treatment. In refractory chronic urticaria, patients can be referred to subspecialists for additional treatments, such as omalizumab or cyclosporine. More than one-half of patients with chronic urticaria will have resolution or improvement of symptoms within a year.