A new appreciation for germs?

It’s enough to cause a shudder among many parents, whose first instinct is to protect kids from dirt and germs. But new research is pointing to an odd paradox — children exposed to different germs at a very young age were less likely to develop asthma in early childhood.

 The study, published online last week in the Journal of Allergy and Clinical Immunology, found that young children exposed to some pretty disgusting bacteria, including those from cockroaches and mice, were less likely to suffer from allergies and asthma later.

The findings build on earlier research driving one of the most popular theories of the growing problem of atopic disorders such as asthma, allergic rhinitis and eczema, said Dr. Jesus Guajardo, associate professor of pediatrics at UT Health Science Center San Antonio, who is board certified in both in pediatric pulmonology and allergy and immunology.

“Researchers are starting to believe that excessive use of cleaners, antibiotics, food processing and so on, leading to hyper-clean environments, may be detrimental to humans by promoting the development of allergies,” said Guajardo, who wasn’t involved in the study. “Interestingly, this effect on the immune system is only found during the first years of life — from conception to one or two years — as exposure later in life may be linked with worse allergy symptoms in allergic individuals.”

In other words, early exposure to germs helps shape our immune systems.

So should parents stop cleaning the house? Invite a small army of dogs, cats, mice and cockroaches to move in? Probably not. The cause and effect is complicated, experts say, and those same germs that might help prime the immune system at the start of life, can be harmful to some pretty soon afterward.

“The interactions are complex and it is not as simple as buying a dog and eating unprocessed food in order to prevent allergies,” Guajardo said.

In the new study, researchers looked at children’s exposures to allergens from cats, cockroaches, dogs, dust mites and mice. They then compared those exposures to allergic reactions, including both wheezing episodes and skin-prick tests.

Cumulative exposure to allergens from cats, mice, cockroaches and dust mites were linked during the children’s first three years of life to more allergic reactions. Dog allergens didn’t seem to cause the same reaction. However, when the researchers looked at just the first year of life, they found a different story. Kids with a lot of exposure to cockroach and mouse allergens had less wheezing and allergic reaction by age 3.

“It seems that have a critical period in our lives in early childhood where if we are not exposed to the common load of bacteria found in dust, dirt and unprocessed food, then the immune system goes haywire and starts responding in an abnormal fashion to non-pathogenic elements,” Guajardo said. “This response leads to a hyper-responsiveness found in allergic disorders.”