Fructooligosaccharides (FOS) are a prebiotic supplement, which can enhance immunological responses in the host to activate mucosal immunity probably through regulation of gastrointestinal microflora. Nonetheless, the therapeutic potential of prebiotics on allergic pathologies has not been fully elucidated. Therefore, the purpose of this study was to evaluate the preventive and therapeutic effects of dietary supplementation with FOS on a murine model of allergic peritonitis induced by ovalbumin (OVA). Male C3H/HeN mice were intraperitoneally administrated with OVA (1 mu g) bi-weekly (Day 0-42, total four times) and were fed a diet containing 0 or 2.5% FOS ad libitum (Day 7-43). At Day 43, mice were killed and several parameters were evaluated. As results, supplementation with FOS alleviated OVA-related peritoneal inflammation characterized by trafficking of polymorphonuclear leukocytes such as eosinophils and neutrophils in the peritoneal cavity. Also, FOS significantly suppressed the protein level of interleukin (IL)-5 and eotaxin in the peritoneal lavage fluid elicited by OVA. In addition, a FOS-supplemented diet significantly reduced the serum allergen specific-IgG(1) level, whereas it significantly increased total IgA levels in the cecal contents as compared with a control diet in the presence of OVA. These results suggest that dietary supplementation with FOS can prevent/ameliorate allergic peritoneal inflammation induced by OVA. The efficacy can at least partially be associated with the regulation of 1g class switching and inhibition of the local expression of IL-5 and eotaxin. (C) 2012 Elsevier Inc. All rights reserved.