An altered microbial exposure may be partly responsible for the increase of allergic diseases in populations with a western lifestyle. Activation of the immune system by microbes early in life is probably required for an accurate maturation of the immune system. Probiotics, live bacteria which are considered to confer health when ingested, have been suggested to prevent eczema and sensitisation infants.

The aim of this study is to assess the effect of oral supplementation with the probiotic bacterium Lactobacillus reuteri in infancy on the development of allergic disease and sensitisation during the first 2 years of life and to examine mechanisms possibly underlying eventual effects on allergic manifestations.

A follow up was performed at 7 years of age.

An altered microbial exposure may be partly responsible for the increase of allergic diseases in populations with a western lifestyle. Activation of the immune system by microbes early in life is probably required for an accurate maturation of the immune system. Probiotics, live bacteria which are considered to confer health when ingested, have been suggested to prevent eczema and sensitisation infants.

The aim of this study is to assess the effect of oral supplementation with the probiotic bacterium Lactobacillus reuteri (L. reuteri) in infancy on the development of allergic disease and sensitisation during the first 2 years of life and to examine mechanisms possibly underlying eventual effects on allergic manifestations. In the study the development of allergic disease will also be related prospectively to immunological, nutritional and environmental factors.

The study is a prospective double-blind placebo-controlled multicenter trial, comprising 232 families with allergic disease. The families are recruited at the antenatal clinic, and the mothers will receive L. reuteri ATCC 55730 (1 x 100 000 000 colony forming units, Biogaia AB, Stockholm, Sweden) or placebo daily from gestational week 36 until delivery. Their babies then will continue with the same study product from birth until 12 months of age and will be followed up for another year. Clinical follow-up will be done at 1, 3, 6,12 and 24 months of age and telephone interviews at 2,4,5, 8, 10 and 18 months. A questionnaire will be completed on each occasion. Skin prick test will be performed at 6, 12 and 24 months of age. Venous blood will be collected from the umbilical cord and at 6, 12 and 24 months and stored as heparinized plasma or serum until assessment. Peripheral mononuclear blood cells (PBMC) will be separated from the plasma samples before storage. Blood samples will also be collected from the mother and father once during the study. The stool sample will be collected from the mother during the 1 week after delivery and the infant at 5-7 days, 1 month, 3 months, 6 months, 12 months and 24 months of age. Saliva samples will be collected at 3, 6, 12 and 24 months of age and breast milk samples will be collected from the mother 1-3 days and 1 months after delivery. The saliva, breast milk and plasma/serum samples will be stored in -20°C and stool samples and the PBMC in -70°C until assessment.

A follow up was performed at 7 years of age focusing on allergic disease. Spirometry, skin prick test was performed. Of the 188 completing the 2 year follow up, 184 also completed the 7 year follow up.

Inclusion Criteria:

• Pregnant women with history of previous or present allergic disease in at least one member of the immediate family (parents or siblings).
• Expected compliance.
• Written informed consent obtained from parents.

Exclusion Criteria:

• Insufficient compliance, i.e. a consumption of the study product below half of the expected.