Chronic urticaria is a disease consisting of spontaneous pruritic welts, present on all or most days for more than 6 weeks. It is commonly supposed to be allergic in origin, although allergy is not the cause in the majority of cases, and it has therefore been termed 'chronic idiopathic urticaria'. Recent evidence indicates that at least a subset of patients in whom no extrinsic or internal cause can be identified are in fact autoimmune in origin. This is based mainly on the detection of pathogenic autoantibodies to the high-affinity immunoglobulin E receptor FcepsilonR1, which are thought to activate cutaneous mast cells. In this article, we review the evidence that has given rise to this autoimmune 'paradigm' and its impact on diagnosis and management.