Muddy Kids

To all overprotective parents: it is official, early exposure to germs is beneficial for your kids. So let them go outside and play in the mud!!!!

In a study published last week in the Science journal (on the 22^nd of March), researchers have shown in mice that exposure to microbes during childhood protect children from developing asthma and other diseases such as inflammatory bowel disease.

Immunologists think that children’s susceptibility to allergies and other autoimmune disorders may be due to the lack of exposure to germs. They consider an early exposure to bacteria and microbes as an important feature for the healthy development of youngsters’ immune system, which in turn shields them against asthma and other allergies in later life. This theory is called the ‘Hygiene Hypothesis’ and it has now gotten stronger with last week’s findings.

Dr. Richard Blumberg, co-author of the study says, "We have co-evolved with microbes for millions of years. There is a very beneficial role for microbes in health. What our study now shows is the critical importance of those microbes in the earliest periods of life."

Details about the study:

1)     For this study the scientists developed two groups of mice – one germ-free raised under sterile conditions and another one raised under normal laboratory conditions. They found that the animals exposed to germs had a stronger disease fighting immune system. The animals raised in sterile conditions were sicker and had inflammation in their lungs and colon (similar to asthma and bowel problems in humans). The researchers found that this was due to an increase of activity of a special immune cell type called invariant natural killer T cell (iNKT).

2)     Animals exposed to germs in the first weeks of their lives were less vulnerable to infections. Adults didn’t show these beneficial effects. Lack of exposure in early life could not be compensated later on.

3)     The researchers have found that the levels of a protein called CXCL16 were higher in the colon and lung tissues of the sterile mice than in the normal mice and that by blocking that protein they could reduce the number of iNKT and the amount of inflammation in those tissues.

Even thought this study has been made in mice and no humans can ever be that germ-free, it is still extremely important as it opens up a lot of questions about how long this early-exposure window lasts and which microbes are involved. Also, it brings light into a possible mechanism involving the protein CXCL16 and the activity of iNKT, helping immunologist to understand and treat asthma and other autoimmune diseases. 

However, before I finish, I would like to make a quick remark:

When letting your kids going out there and ‘eating of dirt and playing in the mud’, you will always have to be a little bit cautious. If you live in the city, your playgrounds may contain high levels of lead and even if you live in a rural area, you might live near fields that have been treated with soil amendments containing toxic pollutants and antibiotic resistant pathogens. So be cautions, ok? I’m not telling you to just let them loose.

Let’s give this a thought, shall we?

(and by the way, this is NOT an April Fools' prank :0) )