Chronic spontaneous urticaria (CsU) is a frequent dermatological disease that might last for months or years with high impact on quality of life. Known causes are autoreactive phenomena, infections or intolerances, rarely IgE-mediated allergies. One third of CsU patients benefit from a low-pseudoallergen diet. Additionally, it is often discussed, that reducing histamine ingestion alone might improve clinical symptoms and quality of life in CsU-patients despite the uncertain role of the histamine-degrading enzyme diamine oxidase (DAO).