Urticaria is one of the most common dermatological and allergological cutaneous reactions and, compared to other diseases, it is easily recognized by patients and physicians alike. Nevertheless, the disease is highly complex regarding its eliciting causes, its clinical manifestations and its therapy. Thus, a famous New York dermatologist once mentioned that he would rather have a lion than a patient with chronic urticaria walk into his office. This may seem surprising since, to the uninitiated, different types of urticaria look alike, and the pathomechanisms are rather well understood, with mast cells being almost invariably the main effector cells. In 1986, a monograph of the first editor (Prof. Czarnetzki, now with the married name Henz) appeared, giving a detailed and thorough review of the then current state of knowledge regarding all aspects of the disease. Since then, two updates of this book have appeared in the German language, with coworkers of the clinic of Prof. Henz helping in the revision of the various chapters of the old monograph, and with particular emphasis on practical aspects of the disease. The present book is mainly a translation of the second German edition, with only minor updates and with more citations from the literature since the 1986 monograph is no longer available for purchase.