5 Reasons to Let Your Kids Play in the Dirt

A little soil could go a long way for your child’s health.

A young girl gleefully shows off her dirty hands.
A growing body of research indicates that dirt does the body (and brain) good. (Photo: Getty Images)
Originally from Baltimore, Oliver lives and writes on a quiet, tree-lined street in Brooklyn.

Parents always want the best for their children, especially when it comes to keeping them healthy. But the growing focus on hypercleanliness—due in no small part to the constant bombardment of advertising that guilts, shames, and scares parents into buying more products—may do more damage than good. Here are five reasons why it might be fine to let your kids get a little dirty every now and again.

1. Dirt Is Good for the Body

Ever wonder why kids are always putting dirty things in their mouths? According to Jane Brody of The New York Times, there may be an evolutionary reason for such a universal behavior, a finding that science seems to corroborate. Called the "hygiene hypothesis," many researchers have concluded that the millions of bacteria, viruses, and worms that enter the body with every spoonful of soil are necessary for the development of a healthy immune system.

Said Dr. Graham Rook, a professor in the department of infection at the Centre for Clinical Microbiology at the University College London, to U.S. News in 2011: "The bottom line is organisms that were present in mud, untreated water, and feces were with us right from the start of humanity. What has happened over the course of evolution is, because these bugs had to be tolerated, they came to activate the tolerance of the immune system. They are the police force that keeps the immune system from becoming trigger-happy. Basically, the immune system is now attacking things it shouldn't be attacking."

2. Dirt Is Good for the Brain

A 2010 study done by Sage Colleges in Troy, New York, found that a bacterium naturally found in soil, Mycobacterium vaccae, can accelerate learning and brighten moods by stimulating neuron growth and raising serotonin levels. Said Dorothy Matthews, who headed the research, to Mother Nature Network: "We found that mice that were fed live M. vaccae navigated the maze twice as fast and with less demonstrated anxiety behaviors as control mice."

Scientists are already experimenting with using the bacteria as a possible treament for depression. In one study, lung cancer patients who were injected with killed M. vaccae reported better quality of life and less nausea and pain. And now science thinks it knows how M. vaccae works: according to Discovery Magazine, the bacteria boosts and buoys moods by activating the same set of serotonin-releasing neurons in the brain as Prozac.

3. Dirt Is Good for Skin

A 2009 study from the University of California at San Diego discovered that bacteria on the surface of our skin play an important role in combating inflammation of the skin when we're injured. According to the researchers, the bug, called staphylococci, works by dampening down overactive immune responses from the body, which can lead to rashes or cause cuts and bruises to be become swollen and painful. Said Professor Gallo, who led the research: "These germs are actually good for us."

4. Dirt Fights Allergies and Asthma

On Monday, researchers at Harvard Medical School published yet another study showing the health benefits of dirt. Studying two groups of mice—one that had been exposed to microbes and one that had been raised in germ-free environments—they found that the group with early-life microbe exposure had siginificantly lower numbers of inflammatory immune cells in the lungs and colon, giving them a better chance at avoiding asthma and inflammatory bowel diseases later in life.

Said researcher Dr. Richard S. Blumberg in a press release: "These studies show the critical importance of proper immune conditioning by microbes during the earliest periods of life. Also now knowing a potential mechanism will allow scientists to potentially identify the microbial factors important in determining protection from allergic and autoimmune diseases later in life."

5. Dirt Is Outdoors

In Richard Louv's 2005 book, Last Child in the Woods, he writes that a new generation of children is suffering from "Nature Deficit Disorder" as they gravitate from physical experiences in the natural world to more solitary, unstructured activities, like playing videogames. Said Louv in an interview with Grist: "When you think about it, for tens of thousands of years children spent much of their childhood playing or working in natural settings. Within the space of two or three decades in Western society, particularly in the United States, that’s in danger of ending. This is a radical change in a very short period of time. It’s got to have important, perhaps profound implications for mental health, physical health, and spiritual health—for who we are."

Whether or not Louv is correct, research continues to show how hard-wired we are to live in the natural world. A 2008 study at the University of Michigan found that memory performance and attention spans improved by 20 percent after subjects spent an hour out in the nature. Another study from University of Pennsylvania found that hospital patients recover faster and need less pain medication when they are in rooms with views of the trees instead of plain walls or brick. It's clear we all need regular doses of the outdoors, children most of all.

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