Cetirizine, one of the most commonly used antihistamines for the treatment of allergic diseases, possesses some anti-inflammatory properties. Despite its common use, the effect of cetirizine on the production of cytokines from peripheral blood mononuclear cells (PBMCs) needs further clarification. The aim of this study was to investigate whether cetirizine changes interleukin (IL)-10, (IF)-gamma and IL-4 production from PBMCs in children with allergic rhinitis. Thirteen children with allergic rhinitis sensitized to house dust mite (HDM) were treated with cetirizine for four weeks. Blood samples were drawn just prior to the treatment, on the last day of the treatment and two weeks following the cessation of treatment The cytokine production from PBMCs was tested in the presence or absence of HDM allergen and measured by ELISA assay. An augmentation in IL-10 production was observed in PBMCs at the 4th week of cetirizine treatment (p<0.05). Furthermore, a significant increase in IFN-gamma production was observed following the therapy. IL-4 release did not change at all time points tested. In addition, IFN-gamma/IL-4 ratio increased following cetirizine treatment. Cetirizine induced a shift in the human Th1/Th2 cytokine balance toward a Th1 type response by increasing IFN-gamma production and augmenting suppressor cytokine release (IL-10). We concluded that apart from its known antihistaminic properties, cetirizine may modulate allergic inflammation while the patients are on regular treatment schedules.