Urticaria and angioedema are 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, and anaphylaxis must be ruled out if urticaria or angioedema is present. 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 when and if triggers are identified. The first-line pharmacotherapy is second-generation H1 antihistamines, which can be titrated to greater than standard doses.