A placebo-controlled, single-blind study was conducted to evaluate the effects of Lactobacillus acidophilus strain L-92 (L-92) on the symptoms of Japanese cedar-pollen allergy. This study was carried out during the 2002 and 2003 seasons of Japanese cedar pollination. Twenty-three in-house volunteers were asked to drink 100 ml of heat-treated milk fermented with L-92 containing 5 x 10(10) of the bacteria, twice a day, for 6 consecutive weeks. A similar study was carried out during the 2003 season for 10 weeks, but the daily dose of bacteria was 2 x 10(10). A significant improvement of the ocular symptom-medication score (SMS) was observed in 2002 and of the score of distress of life in 2003. These data show that a daily oral intake of not less than 2 x 10(10) heat-treated L-92 cells improved the symptoms of Japanese cedar pollinosis, thereby contributing to reduce the dose of concomitant medications. However, no blood parameter was significantly affected in these trials.