The cause of promiscuous activation of skin mast cells in chronic 'idiopathic' urticaria has long defied explanation Mast cells are capable of being activated by a number of different ligands, both involving the high-affinity IgE receptor (Fc epsilon RI alpha) and independently of it. Recently, evidence has emerged that a substantial subset of chronic urticaria patients, representing 25-50% of the total, possess functional (histamine-releasing) autoantibodies of the IgG isotype which appear to be pathogenic in these patients. A smaller number (no more than 5% of the total) possess functional anti-IgE autoantibodies, The specificity of the antibodies is reviewed in the context of the genetic background of these patients. Screening tests and confirmatory laboratory tests are critically discussed, together with implications for both non-specific and specific immunotherapy.
