It's official. Kids need to get dirty.  

It's something that all kids seem to know instinctively and most parents need to be reminded of. A little dirt is a good thing. And a new study has finally found that exposure to dirt might just make our kids healthier in the long run.  

Health experts have known for years that kids who grow up on farms are less likely to have immune system disorders such as asthma, allergies and inflammatory bowel disease than kids who grow up in cities. It's called the "hygiene hypothesis," but even though it's generally accepted, health experts have never understood why it works — until now.  

A new study from an international team of researchers led by scientists at Brigham and Women’s Hospital may finally have found a biological explanation for the hygiene hypothesis. The study, published last week in the journal Science, found that exposure early in life to microbes helped to train certain immune cells to resist disease later in life. Exposure to those same microbes as an adult did not have the same effect.

The immune cells affected were generally those in the lungs and intestines. No microbe exposure meant that the immune cells were not properly "trained," leading to respiratory and digestive disorders later in life. 

So there you have it. A little dirt early in a child's life can help protect him from all sorts of diseases. Go ahead, toss out that bottle of Germ-Ex and let your kids play in the dirt.

Need a little inspiration? Here are 5 great ways to get kids outside.

Why kids need dirt to stay healthy
New study confirms the 'hygiene hypothesis' — that kids need exposure to dirt early in life to stay healthy.