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It's the basic nature of young children to touch the very things in their environment that their parents find most disgusting. Just try to keep your 1-year-old from sticking the dog's bone in her mouth!

Epidemic-scale flu seasons have health authorities imploring regular hand washing, and with talk of sanitizer gel like it was liquid gold, it's tough not to worry about what your children are getting into and the ultimate impact it will have on their health.

Infectious diseases are a legitimate cause for concern, but some would argue that our society has gone overboard when it comes to protecting our kids from germs.

How clean an environment do our kids really need for good health? Here's what experts told WebMD.

Hygiene Hypothesis

A mounting body of research suggests that exposing infants to germs may offer them greater protection from illnesses such as allergies and asthma later on in life.

This line of thinking, called the "hygiene hypothesis," holds that when exposure to parasites, bacteria, and viruses is limited early in life, children face a greater chance of having allergies, asthma, and other autoimmune diseases during adulthood.

In fact, kids with older siblings, who grew up on a farm, or who attended day care early in life seem to show lower rates of allergies. 

Just as a baby's brain needs stimulation, input, and interaction to develop normally, the young immune system is strengthened by exposure to everyday germs so that it can learn, adapt, and regulate itself, notes Thom McDade, PhD, associate professor and director of the Laboratory for Human Biology Research at Northwestern University.

Exactly which germs seem to do the trick hasn't yet been confirmed. But new research offers clues.

In a recent study, McDade's team found that children who were exposed to more animal feces and had more cases of diarrhea before age 2 had less incidence of inflammation in the body as they grew into adulthood.

Inflammation has been linked to many chronic adulthood illnesses, such as heart disease, diabetes, and Alzheimer's.

"We're moving beyond this idea that the immune system is just involved in allergies, autoimmune diseases, and asthma to think about its role in inflammation and other degenerative diseases," McDade says. "Microbial exposures early in life may be important… to keep inflammation in check in adulthood."

Purging Germs: Health Booster or Bad Idea?

Most of the germs lurking about our environment and that live on our bodies are not only harmless; they've been with us for millennia, says Martin Blaser, MD, professor of internal medicine at New York University. 

As human behavior has changed over the past half century, many microbes, such as some that live in the gut, are disappearing.

"These perform important physiological functions but because of modern life they are changing and some are disappearing," Blaser says. "Those disappearances have consequences -- some good, some bad."

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