Infants who encounter a wide range of bacteria are less at risk of developing allergies later in life. "In our study of over 400 children, we observed a direct link between the number of different bacteria in their rectums and the risk of development of allergic disease later in life," says Hans Bisgaard, professor of children's diseases, University of Copenhagen, who led the study. "So it makes a difference if the baby is born vaginally, encountering the first bacteria from its mother's rectum, or by caesarean section, which exposes the newborn baby to a completely different, reduced variety of bacteria. "This may be why far more children born by caesarean section develop allergies. I must emphasise that there is not one single allergy bacteria," Bisgaard points out, according to a university statement. In the womb and during the first six months of life, the mother's immune defences protect the infant. Bacteria flora in infants are therefore probably affected by any antibiotics the mother has taken and any artificial substances she has been exposed to. "Our new findings match the large number of discoveries we have also made in the fields of asthma and hay fever," Bisgaard explains. Like allergies, they are triggered by various factors early in life. The researchers gathered their data from unique material consisting of 411 children whose mothers have asthma.