Environmental Microorganisms and Childhood Asthma

This past week, there was discussion on the internet about an article entitled “Exposure to Environmental Microorganisms and Childhood Asthma” that was written by Markus Ege, MD and colleagues (New England Journal of Medicine 2011;364:701-709). The gist of the article was that children who grow up in environments, such as traditional farms, that expose them to a wide range of microbes (i.e., germs such as bacteria and fungi) seem to be protected from childhood asthma and certain types of allergic reactions.

The authors did a new study to compare children living on farms with a reference group made up of children who grew up in non-farm environments, looking at the prevalence of asthma and atopy in both groups. Atopy is the genetic tendency to develop “classic” allergic diseases, such as skin rashes, hay fever, asthma, etc.; commonly felt to be due to immunoglobulin E [IgE] generated in response to common environmental proteins that originate from sources such as house mites, grass pollen and certain foods. In particular, the study looked at the diversity of the microbes to which these children were exposed. They found that among children living on farms, there was a lower prevalence of asthma and atopy and that these children were exposed to a greater variety of environmental microbes than were those in the reference group. The greater the diversity of microbes, it seems, the less the risk of asthma. Furthermore, exposure to certain microbes seemed to be particularly influential in this protective effect.

The presumption is that exposure to the germs is mostly derived from inhalation, rather than eating or drinking them, or having them enter the body in some other manner. Whether or not the children actually become infected by these germs during the process could not be determined. The authors pondered whether or not these children would show a lower incidence of autoimmune diseases, such as type 1 diabetes and Crohn’s disease, later in life.

It would be very interesting to know if other outdoor environments, and not just farms, create this same effect. This study implies that it is good to be outdoors, and that exposure to dust and dirt is not all bad. There is no question that inhaling dirt and exposure to certain germs in the outdoor setting can cause disease, so no one is making a leap to “dirt therapy.” The take-home message is that there are good and bad aspects to everything. Exposure to allergens can sensitize a person and cause them to have a severe allergic reaction upon subsequent exposure. But in this current observation, it is possible that certain types of exposure in children may offer protection against other types of allergic diseases and atopy. For reasons of immediate hygiene and personal and group protection against diarrheal diseases, you should always wash and attempt to disinfect your hands before you eat or handle food, and if you get dirt and dust in your mouth, spit it out and rinse it away as best possible.