Pathology and classification of urticaria

Chronic urticaria is defined as daily or almost daily urticaria for more than 6 weeks. Chronic urticaria is normally subdivided into physical urticaria (wheals evoked by a physical stimulus such as pressure friction or cold contact) and spontaneous urticaria. A patient with a history of less than 6 weeks is traditionally designated as having acute urticaria. Patients with chronic spontaneous urticaria have an increased frequency of HLA-DR and HLA-DQ alleles characteristically associated with autoimmune disease. Some of these patients have functional anti-FceR1 and/or anti-IgE autoantibodies which are considered to be the cause of the urticaria.