Effect of Lactococcus lactis subsp. cremoris YRC3780 on birch pollinosis: a randomized, double-blind, placebo-controlled clinical trial

In a randomized, double-blind, placebo-controlled trial, 114 patients with birch pollinosis received Lactococcus lactis subsp. cremoris YRC3780 (YRC3780) powder (n = 28, 29, 28, in each dose group) or a placebo (1 g starch powder, n = 29) daily for 12 weeks during the 2016 pollen season. Patients self-recorded their symptom and medication scores daily, and blood samples were evaluated every 4 weeks throughout the treatment observation periods. Symptom and medication scores during the intake period were grouped into 6 consecutive periods of 2 weeks each, and average values were compared between periods. In the YRC3780-treated groups, medication scores were significantly lower than scores in the placebo group during intake periods 3 (P < 0.05). In addition, blood levels of thymus- and activation-regulated chemokines (TARC) at 12 weeks were significantly decreased. Consuming at least 109 CFU of YRC3780 daily ameliorated the symptoms of birch pollinosis, likely by improving Th1/Th2 balance.