ABSTRACT Chronic urticaria can be defined as the occurrence of widespread daily or nearly daily wheals for at least 6 weeks, which may be accompanied by angioede- ma. It is a disease with a considerable impact on pa- tients’ quality of life. Furthermore, these patients may undergo extensive laboratory evaluations seek- ing a cause only to be frustrated when none is found. There is no curative treatment for this disorder and we do not understand the mechanisms that lead to the onset of disease. However, in recent years there have been significant advances in the understanding of some of the molecular mechanisms that cause cu- taneous inflammation that is manifest as urticaria and angioedema. In this review we will summarize our recent contributions to this field and try to offer insights regarding future directions for research. Key words: Chronic urticaria. Cutaneous inflamma- tion. Angioedema. Interleukins. Lymphocytes Th1-Th2. Mast cells. Basophils. INTRODUCTION Chronic urticaria can be defined as the occurrence of widespread daily or nearly daily wheals for at least 6 weeks 1 , which may be accompanied by angioede- ma. While the wheals are transient, the resolution of angioedema is slower and could take up to 72 hours. The natural course of chronic urticaria is self-limited, with spontaneous remissions and occasional relap- ses 2 . We recently calculated a 0.6 % (95 % CI: 0.4-0.8) prevalence in a population study 3 . Chronic urticaria has a considerable impact on pa- tients’ quality of life 4,5 . In a recent national survey on patients attending an Allergy Department, chronic ur- ticaria was the disease with the greatest impact on quality of life of all the allergic diseases. Furthermore, these patients may undergo extensive laboratory evaluations seeking a cause only to be frustrated when none is found. There is no curative treatment for this disorder and we do not understand the mechanisms that lead to the onset of disease. However, in recent years there have been significant advances in the understanding of some of the molecular mechanisms that cause cu- taneous inflammation that is manifest as urticaria and angioedema. In this review we will summarize our recent contributions to this field and try to offer insights regarding future directions for research. Malmros 6 was the first to report the ability of au- tologous serum to elicit a positive skin test, yet his report published in 1946 was largely forgotten. In 1982 when Leznoff et al reported a 15 % prevalence of antithyroid antibodies in patients with chronic ur- ticaria 7 a role for autoimmunity in disease pathoge- nesis was again considered. Later observations re- ported a 5-10 % incidence of functional anti IgE antibodies again suggesting that autoimmunity might have a role 8 in the disease. Then the autologous skin Allergol et Immunopathol 2007;35(2):57-61 Chronic urticaria: What is new, where are we headed M. Ferrer a and A.P. Kaplan b a Department of Allergy, Clinica Universitaria, Universidad de Navarra, Pamplona, Spain. b National Allergy, Asthma, & Urticaria Centers of Charleston, Charleston, SC, USA. Correspondence: Dra. Marta Ferrer Department of Allergy and Clinical Immunology Clinica Universitaria Universidad de Navarra Pio XII, 36 31008 Pamplona, Spain Phone: + 34948255400 Fax: + 34948296500 E-mail: mferrerp@unav.es