According to a recent study from the University and the University Central Hospital of Helsinki, Finland, no allergy-preventive effect is extended to age 5 years by perinatal supplementation with probiotics in babies at risk for developing allergies; protection is conferred only to Cesarean section babies.
Childhood allergies have increased significantly in industrialized countries during the past few decades. Researchers theorize that this rising incidence is the result of a lowered exposure to bacteria in early childhood. This exposure to microbes appears to be essential in jump-starting the immune system to develop healthy pathways that do not result in allergic conditions.
Additionally, it's been observed that infants who develop allergies have intestinal bacteria that are distinctly different from those of non-allergic infants, suggesting that the type of intestinal microflora is an important factor in forming allergic conditions.
In a study published in the Journal of Allergy and Clinical Immunology (online January 2009) researchers from the University and University Central Hospital of Helsinki conducted a clinical trial of more than 1200 mothers whose infants would be at high risk to develop allergies. During the last month of their pregnancies, the mothers took daily doses of a probiotic mixture or a placebo, and their infants were given the same probiotic mixture plus a prebiotic or a placebo for the first 6 months of their lives. The children were followed for 5 years and evaluated for incidence of allergic diseases.