When your patients are itching to see you: not all hives are urticaria.

When patients present with itching and the perception that they have hives, what other processes can mimic urticaria? With the exception of urticarial vasculitis, urticaria typically lasts less than 24 to 36 hours at one site. A rash that persists longer should raise the suspicion of another inflammatory process. When the hive-like rash does not respond to antihistamines, a biopsy may reveal an alternative diagnosis. All biopsies should also be submitted for immunofluorescence to exclude atypical presentations of inflammatory bullous disease presenting with urticaria. However, even biopsies can be subject to misinterpretation and if the clinical picture does not support the biopsy, an alternative consultation with a dermatopathologist may be required. The extent of the laboratory and radiologic evaluation should be dictated by the clinician's suspicion of alternative causes for the hive(s) because rarely malignancies may present with urticaria. Common things are indeed common with urticaria and the more urticaria does not appear to be typical, the more often the clinician should consider alternative diagnoses.