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Another Study Links Getting Dirty to Good Health


Parents know that their kids need time outside, but not all of us are happy when they play in the dirt. If your kid would rather play in dirt, rocks, and mulch at the playground than use the slides and swings, be happy; it is good for their health! Studies show that dirt makes us happy and healthy.

If you ever felt good for playing in the dirt, it wasn’t just your imagination. A 2007 study showed that a specific soil bacterium, Mycobacterium vaccae, causes a release of serotonin, a neurotransmitter that makes us feel happy.

A new study found that playing in dirt can prevent asthma and allergies by promoting the development of pulmonary macrophages (pathogen-trapping cells found in the lungs). The study also found that mice who were in a sterile environment did not develop pulmonary macrophages, and they developed asthma. Mice in the study did not get asthma when the macrophages were transferred to them.

Scientists say that the immune system is trained by early childhood exposure (by age 3-4) to foreign particles. The study supports this theory since exposure to foreign particles was necessary for the formation of cells (macrophages) responsible for catching foreign particles in future interactions. Without the macrophages, irritants cause allergic reactions and asthma instead of being captured and killed.

Graham Rook, a professor of medical microbiology at University College London says that we need exposure to our ‘old friends,’ the microbes that we were in contact with during early hunter-gatherer times when our immune systems were evolving. Our “old friends” are thought to be “friendly” microbes that we encounter in our daily lives, not infectious pathogens. Rook states “If your child has been out in the garden and comes in with slightly grubby hands, I, personally, would let them come in and munch a sandwich without washing.”

Scientists agree that early exposure to microbes is healthy, but they worry public confusion about microbes could lead to more disease. Sally Bloomfield, chair of the International Scientific Forum on Home Hygiene and professor at the London School of Hygiene and Tropical Medicine has expressed her concern “I’ve even seen things in the media saying we shouldn’t wash our hands. What the hell are they talking about?”

Children should be taught the difference between microbes that cause infectious diseases – such as those that could be picked up out in public or by touching raw meat – and the beneficial microbes that can be found in dirt or around the house. Keeping a sanitary household and limiting outdoor play has been found to prohibit necessary exposure to beneficial microbes. These studies bring the meaning of dirty to question and if dirt can really be called dirty, after all.