Among the many attempts to classify urticaria, 2 categories have been accepted worldwide, namely according to time course into acute (shorter than 6 weeks) and chronic urticaria (longer than 6 weeks) and a classification according to etiopathophysiology.

A special subgroup is the physical urticarias where wheals are elicited via specific physical (mechanical, temperature, radiation) stimuli. In many forms of chronic urticaria, psychosomatic influences play a role. Despite great progress in modern immunology and allergology, chronic urticaria still remains a challenge for doctors and patients.

• J. Ring, Department Dermatology and Allergology Biederstein, Christine Kühne-Center for Allergy Research and Education (CK-CARE), Technische Universitaet Muenchen, Biedersteiner Str. 29, D-80802 München, Germany
• M. Grosber, Department Dermatology and Allergology Biederstein, Christine Kühne-Center for Allergy Research and Education (CK-CARE), Technische Universitaet Muenchen, Biedersteiner Str. 29, D-80802 München, Germany