Aim: To investigate whether birch pollen allergy symptoms are linked with gut microbiota changes and whether probiotics have an effect on these.
Methods: Forty seven children with confirmed birch pollen allergy were randomized to receive either a probiotic combination of Lactobacillus acidophilus (L. acidophilus) NCFM (ATCC 700396) and Bifidobacterium lactis (B. lactis) Bl-04 (ATCC SD5219) or placebo in a double-blind manner for 4 mo, starting prior to onset of the birch pollen season. Symptoms were recorded in a diary. Blood samples were taken for analysis of cytokines and eosinophils. Fecal samples were analysed for microbiota components, calprotectin and IgA. Nasal swabs were taken for analysis of eosinophils.
Results: The pollen season induced a reduction in Bifidobacterium, Clostridium and Bacteroides which could not be prevented by the probiotic intervention. During the intervention, significantly higher numbers of B. lactis 11.2 x 10(7) +/- 4.2 x 10(7) vs 0.1 x 10(7) +/- 0.1 x 10(7) bacteria/g feces (P < 0.0001) and L. acidophilus NCFM 3.5 x 10(6) +/- 1.3 x 10(6) vs 0.2 x 10(6) +/- 0.1 x 10(6) bacteria/g feces (P < 0.0001) were observed in the probiotic group compared to the placebo group. During May, there was a tendency for fewer subjects, (76.2% vs 95.2%, P = 0.078) to report runny nose, while during June, fewer subjects, 11.1% vs 33.3%, reported nasal blocking in the probiotics group (P = 0.101). Concomitantly, fewer subjects in the probiotic group had infiltration of eosinophils in the nasal mucosa compared to the placebo group, 57.1% vs 95% (P = 0.013). Eye symptoms tended to be slightly more frequent in the probiotic group, 12.5 d [interquartile range (IQR) 6-18] vs 7.5 d (IQR 0-11.5) (P = 0.066) during May. Fecal IgA was increased in the placebo group during the pollen season; this increase was prevented by the probiotics (P = 0.028).
Conclusion: Birch pollen allergy was shown to be associated with changes in fecal microbiota composition. The specific combination of probiotics used was shown to prevent the pollen-induced infiltration of eosinophils into the nasal mucosa, and indicated a trend for reduced nasal symptoms.