By Chelsea Karnash

BALTIMORE, MD (CBS) – With a new baby at home, it can be difficult for many parents to quell their urge to sanitize every surface.

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But new research from Johns Hopkins suggests you might want to put away those antibacterial wipes and let a little dirt linger.

According to researchers in the Division of Allergy and Immunology at the Johns Hopkins Children’s Center, early exposure to bacteria and allergens can shape children’s immune systems and actually prevent asthma and wheezing.

The study looked at nearly 500 newborns in Baltimore, Boston, New York and St. Louis whose health was tracked over the course of three years. Investigators reportedly visited the homes where the babies were living and tested their allergen and bacteria levels, then periodically tested the babies’ for allergies and wheezing. They also surveyed the parents and gave the babies physical exams, and analyzed dust collected from the homes.

Surprisingly, exposure to things like mouse and cat dander and (ugh) roach droppings within the first year of the child’s life actually seemed to offer that child protection from allergies. Furthermore, that protective effect was additive, meaning that infants exposed to all three allergens were less likely to wheeze or have allergies than those who came into contact with just one.

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Johns Hopkins researchers say the new findings back up previous studies, which showed children raised on farms have lower rates of allergies and asthma due to their exposure to bacteria in soil. But the study’s leaders also say timing is everything. While children exposed to allergens during their first year seemed to ward off issues, those who were exposed to high levels after that had higher rates of wheezing, asthma and allergies.

“Our study shows that the timing of initial exposure may be critical,” says study author Robert Wood, chief of the Division of Allergy and Immunology at the Johns Hopkins Children’s Center, on The Hub, the school’s news site. “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.”

In other words, a little dirt – at least during infancy – won’t hurt and could actually help keep your child’s immune system strong.

The research was published Friday in the Journal of Allergy and Clinical Immunology. For more information, click here.

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