BACKGROUND Chronic urticaria has been described in patients with Helicobacter pylori infection. Despite numerous studies, the correlation between H. pylori infection and chronic urticaria is doubtful. Our study was performed to determine the prevalence of H. pylori infection in autoimmune urticaria and in patients suffering from autoimmune urticaria and autoimmune thyroiditis. METHODS The authors widely investigated 48 patients. The examinations were extended principally to autologous serum skin test, antithyroid antibodies, and the presence of H. pylori infection as well as detection of antibodies against H. pylori. RESULTS Out of the 48 patients, 26 were regarded as having autoimmune origin. The prevalence of antithyroid antibodies was different in the two groups of patients with urticaria. There were 11 patients (42.3%) in the autoimmune group compared with three patients (13.6%) in the nonautoimmune group with antithyroid peroxidase antibody (P = 0.03). The difference in the prevalence of H. pylori infection was significant between autoimmune urticaria with and without thyroid autoimmunity (90.9% vs. 46.7%; P = 0.02). Autoimmune thyroiditis was connected with CagA +H. pylori strains, as the H. pylori- specific IgG antibodies revealed significant differences in a prevalence of 120 kDa (P < 0.05). CONCLUSIONS The authors observed a relationship between autoimmune urticaria and autoimmune thyroiditis. The results strengthen the possibility of cross-reactivity being triggered between CagA plus H. pylori strains and some other organ-specific autoimmune diseases such as autoimmune urticaria and autoimmune thyroiditis. This indicates a possible role of H. pylori in triggering autoimmune urticaria in at least a select group of patients.