Probiotics are perceived to exert beneficial effects in the prevention and treatment of allergic diseases via modifying the gut ecosystem. The aim of this study was to assess whether ingestion of fermented milk containing Lactobacillus paracasei-33 (LP-33), a strain newly isolated from the human intestinal tract, can improve the quality of life of patients with perennial allergic rhinitis. In a randomized, double-blind, placebo-controlled trial, we gave patients fermented milk with (n = 60) or without (n = 20) the addition of LP-33 (2 x 10(9) colony-forming units per bottle) for 30 days. A modified questionnaire concerning pediatric rhinoconjunctivitis quality of life was administered to all subjects or their parents at each clinical visit. Scores for the overall quality of life significantly decreased in the LP-33 group as compared with the placebo group, in both frequency (-16.02 +/- 2.14 vs. -7.27 +/- 3.55, respectively; p = 0.037) and level of bother (-16.35 +/- 2.33 vs. -6.20 +/- 3.13, respectively; p = 0.022) after the 30-day treatment. Subjects reported no severe adverse effects such as fever, abdominal pain, or diarrhea. The results suggest that ingestion of LP-33-fortified fermented milk for 30 days can effectively and safely improve the quality of life of patients with allergic rhinitis, and may serve as an alternative treatment for allergic rhinitis.