Anti-bacterial soap. Germ-killing sprays and disinfectants. Antibiotics. Air purifiers.

In our attempt to make everything clean, dirt and germs have become the enemies of the modern lifestyle. But is our obsession with being clean damaging to our health?

Past research shows that we may just be cleaning ourselves sick by removing our exposure to the healthy germs and bacteria that help strengthen our immune systems. It's called the hygiene hypothesis and it goes something like this: Children who have less exposure to viruses and illnesses are more prone to develop allergies and asthma later in life. On the flip side, children who grow up in rural areas, around animals, or in larger families tend to have a lower incidence of allergies and asthma than their peers.

The theory behind the hygiene hypothesis is that when children are not exposed to small doses of viruses, bacteria, and parasites, their immune systems are not able to practice fighting off these infections. And without practice, the immune system never learns when and how to fight. So when it does come across a foreign substance, it overreacts by triggering asthma and allergic reactions.

And fresh research seems to back up this claim. Dr. Robert Woods, chief of the Division of Allergy and Immunology at the Johns Hopkins Children's Center in Baltimore, co-authored a study about the effects of early-life exposure to allergens, which found that children exposed to specific allergens in their first year of life were less likely to experience specific allergy symptoms (like wheezing) later in life.

So while our germ-obsessed lifestyle may mean that our children will suffer fewer instances of cold and flu, it also means that we are exposing ourselves them to a higher risk of asthma and allergies.

Does this mean we should stop washing our hands? Or make our kids play in the mud?

Unfortunately, it's not as simple as that.

For one thing, exposure to certain viruses and bacteria really can make our kids horribly sick. For another thing, health experts aren't really sure when in a child's development the exposure needs to occur to strengthen the immune system. Much more research needs to be completed so that doctors can better understand the hygiene hypothesis and our role in preventing illness.

But one thing they do know is that a little dirt never hurt. So don't be afraid to let your kids play outside. And the next time they come down with a sniffle, resist the urge to dose them up with antibiotics. Let those little immune systems do their thing so that they learn when and how to do it.

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