The links between chronic urticaria, IgE sensitization and allergy have been much discussed but little studied. We investigated IgE sensitization and allergy in 128 adult chronic urticaria patients during 2006-2008. During a one-day hospitalisation, the patients answered a standardized questionnaire and underwent blood serum analysis, physical tests and skin prick-tests. IgE sensitization to environmental allergens was defined by the positivity of at least one skin prick test and/or elevated levels of serum IgE ≥ 300 Kui/L. The chronic urticaria was considered allergic if: i) a high correlation between positive skin prick tests to a clinically relevant allergen and the case history was found; ii) complete remission of urticaria occurred within two months of allergen withdrawal. Of 105 patients with interpretable skin prick tests, 46.7% were IgE sensitized. Two patients had clinically relevant positive skin prick tests but their chronic urticaria had many other triggering factors and neither was in complete remission after withdrawal of these allergens. IgE sensitization is higher in chronic urticaria patients than in the global adult population, suggesting that it is one important etiopathogenic factor in chronic urticaria. However, it cannot be considered as the expression of an IgE-mediated allergy but as a chronic inflammatory disease, more frequent in IgE sensitized people and favoured by multiple factors, among which IgE-mediated allergy is exceptional.