Acute and chronic urticaria may be triggered by infection. Streptococci and Helicobacter pylori are the most frequent acute infectious causes. We present two cases in which we cultured Norovirus in the stool of patients with both acute and chronic urticaria. Noroviruses (genus Norovirus, family Caliciviridae) are a group of single stranded RNA, nonenveloped viruses which cause acute gastroenteritis in humans. Norovirus was recently approved as the official genus name for the group of viruses provisionally described as Norwalk-like viruses (NLV). Therapy is symptomatic. Noroviruses should be regarded as possible infectious trigger for dermatologic diseases. In seeking a focus of viral or bacterial infection for skin diseases with unknown origin, stool cultures should be part of the routine evaluation.