Soy sauce (Shoyu) is a traditional fermented seasoning of East Asian countries and available throughout the world. We obtained polysaccharides from raw soy sauce, and showed the anti-allergic activities of these Shoyu polysaccharides (SPS) in vitro and in vivo. The present study determined whether oral supplementation of SPS is an effective intervention for patients with perennial allergic rhinitis. In a 4-week randomized, double-blind, placebo-controlled parallel group study, patients with mild perennial allergic rhinitis were treated with 600 mg of SPS (n=11) or placebo (n=10) each day. After 4 weeks of treatment with SPS, a reduction in symptom scores for runny nose, sore throat, and itchy eyes were significantly changed from the baseline within the group (p<0.05), but no change in these scores was observed over 4 weeks of treatment in the placebo group. However, differences in the symptom scores during the study period were not significantly different between the groups. The total symptom score, calculated from the sum of individual scores, showed a significant difference between the 2 groups after 4 weeks of treatment (p<0.05). The efficacy of global symptoms score, which was defined as the adjusted mean change from baseline during 4 weeks of treatment, also showed a significant improvement in the SPS group (p<0.05). An overall evaluation of the medication's effectiveness after 4 weeks treatment showed significant differences between the SPS- and placebo-treated groups (p<0.05). In conclusion, SPS of soy sauce improved the quality of life for patients with perennial allergic rhinitis, and soy sauce would be useful in an anti-allergic therapy utilizing everyday foods.