Allergic diseases have been on the rise in Denmark in recent decades, and a new study focusing on children and their exposure to bactaria is yielding some partial answers.

Professor Hans Bisgaard, a professor at the University of Copenhaagen, released results of a 12-year study involving 411 children whose mothers have asthma.

Bisgaard says that the amount of bacteria children are exposed to is linked to whether or not children get allergies.

“What matters is to encounter a large number of different bacteria early in life when the immune system is developing and ‘learning,’” he said in a statement.

“The window during which the infant is immunologically immature and can be influenced by bacteria is brief, and closes a few months after birth,” he says.

Key Link

"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," Bisgaard said.

The less intestinal microorganisms there were during infancy, the the greater the risk of allergic disease at school age, he said.

However if there was more “diversity” in bacteria exposure the risk was reduced.

Baby’s Bacteria Exposure at Birth

Bisgaard specifically mentioned one instance when children are first exposed to bacteria: When exiting the mother’s vagina and encountering the mother’s rectum bacteria.

Such exposure helped reduce allergies later on, he said.

"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 new-born baby to a completely different, reduced variety of bacteria. This may be why far more children born by caesarean section develop allergies,”Bisgaard said.

Ironic Discovery

While bacteria has been perceived as a threat to public health, it turns out to be a fundamental part of a healthy life.

The result, Bisgaard, acknowledges, is ironic.

Bisgaard also speculated about what the discovery could mean for other diseases.

“"I think that a mechanism that affects the immune system will affect more than just allergies,” he said. “

“It would surprise me if diseases such as obesity and diabetes are not also laid down very early in life and depend on how our immune defenses are primed by encountering the bacterial cultures surrounding us,” he added.