The cause of urticaria and angioedema often is difficult to ascertain. In most cases the conditions are transient, but a chronic idiopathic form does occur and may be intractable. Acute urticaria and angioedema usually result from an IgE-mediated mechanism; success in treatment depends on recognition of the underlying factor. Chronic urticaria may ultimately necessitate use of corticosteroids. Hereditary angioedema is easily differentiated from idiopathic angioedema by the family history and absence of pruritus.
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