Probiotics prevent IgE-associated allergy until age 5 years in cesarean-delivered children but not in the total cohort

Background: Less microbial exposure in early childhood is associated with more allergic disease later. Allergic children have a different fecal microflora, with less lactobacilli and bifidobacteria. Beneficial effects regarding the development of allergy have been suggested to come through probiotic supplementation. Objective: We sought to study the effect of probiotic and prebiotic supplementation in preventing allergies. Methods: In a double-blinded, placebo-controlled study we randomized 1223 mothers with infants at high risk for allergy to receive a probiotic mixture (2 lactobacilli, bifidobacteria, and propionibacteria) or placebo during the last month of pregnancy and their infants to receive it from birth until age 6 months. Infants also received a prebiotic galactooligosaccharide or placebo. At 5 years, we evaluated the cumulative incidence of allergic diseases (eczema, food allergy, allergic rhinitis, and asthma) and IgE sensitization. Results: Of the 1018 intent-to-treat infants, 891 (88%) attended the 5-year visit. Frequencies of allergic and IgE-associated allergic disease and sensitization in the probiotic and placebo groups were similar: 52.6% versus 54.9% and 29.5% versus 26.6%, respectively, and 41.3% in both. No significant difference appeared in frequencies of eczema (39.3% vs 43.3%), atopic eczema (24.0% vs 25.1%), allergic rhinitis (20.7% vs 19.1%), or asthma (13.0% vs 14.1%) between groups. However, less IgE-associated allergic disease occurred in cesarean-delivered children receiving probiotics (24.3% vs 40.5%; odds ratio, 0.47; 95% CI, 0.23% to 0.96%; P = .035). Conclusions: No allergy-preventive effect that extended to age 5 years was achieved with perinatal supplementation of probiotic bacteria to high-risk mothers and children. It conferred protection only to cesarean-delivered children. (J Allergy Clin Immunol 2009;123:335-41.)