History, with special attention to possible offending exposures and/or ingestion as well as the duration of lesions. Urticarial vasculitis typically persists >72 h, whereas conventional urticaria often lasts <48 h.

• Skin testing to food and/or inhalant antigens.
• Physical provocation, e.g., challenge with vibratory or cold stimuli.
• Laboratory examination: complement levels, erythrocyte sedimentation rate (ESR) (neither an elevated ESR nor hypocomplementemia is observed in IgE-mediated urticaria or angioedema); C1 inhibitor (C1INH) testing for deficiency of C1INH antigen (type 1) or a nonfunctional protein (type 2) if history suggests hereditary angioedema; cryoglobulins, hepatitis B antigen, and antibody studies; autoantibody screen.
• Skin biopsy may be necessary.