Urticaria

I'll keep this short and sweet:  If you want to distinguish between urticaria and urticarial vasculitis, either ask the patient if the lesions last more than 24 hours, or have them come in after having drawn a border around the urticarial lesion, much the same as if you were documenting cellulitic change.  As one of our playas noted, you can also look for petichiae or bruise-like change to sniff out UV, but the easiest way is simply to ask the patient how long they last.