Erythematous plaques and wheals on the legs that, in part, do not blanch on diascopy (compression of the lesional skin with glass), which indicates hemorrhage. This contrasts with urticaria. Also, in contrast to lesions of urticaria, which usually resolve within 24 hours, those of urticarial vasculitis persist for up to 3 days before resolving with residual hyperpigmentation (hemosiderin deposition). Lesions of urticaria change shape in a short time, while those of urticarial vasculitis change slowly. (Used with permission of Dr. Kenneth Greer.)