I remember digging around in the dirt and picking up pill bugs and worms—all without hand sanitizer and hand wipes! If my hands got too dirty, I would just run them under the hose, further exposing myself to who knows what; otherwise, I just waited until I was called inside and used good old soap and water. As a kid I don’t remember being sick very often, so I like to think I have a pretty good immune system and I believe some of it could be due to my exposure to the environment around me.

Anyone born prior to the mid- to late-eighties was likely part of an unknown experiment that became known as the “hygiene hypothesis.” The hygiene hypothesis was first supported scientifically in 1989 by David Strachan in which he suggested early exposure to allergens helps protect the immune system from future allergens.[1] Others have since conducted similar but more aggressive research, such as one in which mice were injected with influenza A virus and Helicobacter pylori to protect against asthma by suppressing natural killer T cells.[2]

This is the premise of the recent study, “Microbial exposure during early life has persistent effects on natural killer T cell function” by Harvard University researchers who compared asthma- and ulcerative colitis-susceptibility of germ-free and normal colonized mice. In their examination of these mice, they made some interesting discoveries:

• Germ-free mice were susceptible to both asthma and ulcerative colitis; whereas normal colonized mice were resistant to both.
• Germ-free mice that were later colonized still remained susceptible to both diseases.
• Germ-free pregnant mice that were colonized just before giving birth delivered babies resistant to both diseases.

The latter finding reminds me of a blog post I wrote previously (Aren't Antibiotics Supposed to Help?) in which I discussed chronic antibiotic use by pregnant mothers, which consequently affects the levels of beneficial bacteria transferred to the baby at birth. Add to this the high rate at which antibiotics are prescribed to children who often don’t even need them and you have a child with a higher susceptibility to illnesses and a less-than-optimal gut flora to help fight off these illnesses.

Granted, times have changed and some germs are much more powerful and resistant these days; but a little dirt doesn’t hurt and it might even be good for the immune system. The best approach is to find balance; too much or too little of anything is never good. Proper hygiene is necessary; however, sanitizing after touching anything and attempting to live in a completely sterile environment may be a bit overboard. This is especially true when many of these sanitizers and the containers they come in may be exposing you to other environmental toxins. So go ahead and inoculate yourself a bit by “playing in the dirt!”

~ Christie Egeston, MS

References

1. Strachan DP. Hay fever, hygiene, and household size. Bmj. Nov 18 1989;299(6710):1259-1260.
2. Chang YJ, Kim HY, Albacker LA, et al. Influenza infection in suckling mice expands an NKT cell subset that protects against airway hyperreactivity. The Journal of clinical investigation. Jan 2011;121(1):57-69.
3. T. Olszak et al., “Microbial exposure during early life has persistent effects on natural killer T cell function,” Science, doi:10.1126/science.1219328, 2012.