Babies exposed earlier in life to germs and dirt are less likely to develop allergies and asthma

A new study suggests urban newborns who share their homes with cockroaches, mice and cats might get the same kind of protection from allergies and asthma that farm children seem to get from the animals in their barns, according to a study published Friday in the Journal of Allergy and Clinical Immunology.

To conduct their research, scientists at Johns Hopkins Children's Center collected data from 467 inner-city newborns, following them for three years and monitoring blood tests for signs of allergies.  Simultaneously, the team also measured the levels of allergens and bacteria in the children's homes.

"What we found was somewhat surprising and somewhat contradictory to our original predictions," said study co-author Dr. Robert Wood, chief of the Division of Allergy and Immunology at the Johns Hopkins Children's Center in Baltimore. "It turned out to be completely opposite -- the more of those three allergens you were exposed to, the less likely you were to go on to have wheezing or allergy."

The researchers noted that their study shows that environmental exposures are significant, especially just after a child is born.

"Our study shows that the timing of initial exposure may be critical," said study author Dr. Robert Wood, chief of the division of allergy and immunology at the Johns Hopkins Children's Center, in a press release. "What this tells us is that not only are many of our immune responses shaped in the first year of life, but also that certain bacteria and allergens play an important role in stimulating and training the immune system to behave a certain way."