Chronic urticaria and blastocystis hominis infection: a case report.

We report a case of a 45 year old woman which fulfilled the criteria of chronic urticaria (remitting and relapsing bouts of erythematous and pruriginuos lesions without angioedema, lasted four months). Cutaneous manifestations were not related to a specific inducing factor, had no benefit from antihystamine and steroid drugs and were associated sometimes with mild gastroentric disorders. Patient was submitted to extensive clinical, laboratory and intrumental investigations which permit to exclude many conditions: allergy to inhalants, food, insects and drug adverse reactions, autoimmune urticaria, autoimmune diseases, neoplastic and infectious diseases. Finally coprocolture disclosed the presence of Blastocystis hominis in stool samples thus permitting to associate urticaria to parasitic infection. Both cutaneous manifestations and mild abdomen disturbs disappeared after appropriate treatment. Despite the high diffusion the aetiopathogenesis of chronic urticaria remains often undefined. A large number of parasites have been correlated with urticaria but few data exist as regards Blastocystis hominis infection; then our findings may add evidence to the role of this parasite in inducing chronic urticaria. Considering that Blastocystis hominis is a modest pathogen for humans, the mechanism is probably the typical one of cutaneous allergic hypersensitivity; antigen parasites induce the activation of specific clones of Th2 lymphocytes, the release of related cytokines and the consequent IgE production.