Several years ago, I was at Toastmasters meeting up in Washington County, New York, and one of the club’s members had brought her <1-year-old to the meeting (not to give a speech, I hasten to add). The child was playing around on the floor of the meeting room, a well-traveled public space that was generally clean-ish, but not as fastidiously sanitized as one would like. In some families I know, children are stored in plastic bubbles until they are 21 and are scarcely allowed to come into contact with any kind of microorganism. But in this case, the child’s mother, who has a background in science, calmly pointed out that her daughter “needed the bacteria.”
Not being a parent (or even apparent), I don’t know what the conventional wisdom vis-à-vis germs and children is today, but back in my day (the early 17th century), we were allowed to wallow in all sorts of filth, although I, being a bit more Felix Ungerish than most children, usually avoided those sorts of things. (I’m told that I also almost failed first grade because I refused to fingerpaint.) Still, while I remember a long litany of childhood colds and flus, after about the age of 12, I very rarely got sick, and even today, a few decades later, the number of colds or flus I’ve had that lasted longer than a day or two can be counted on the fingers of one hand. (Big risk factor: crowded flights from Florida at the end of February. Think of an airplane as a giant flying Petri dish.)
Which is why the latest research on exposure to microbes and other tiny nasties does not
especially surprise me:
With modern plumbing and hygiene, the number of nasty microbes we humans are exposed to has plummeted, while the rate of autoimmune diseases and allergies has shot up.
The so-called hygiene hypothesis holds that
our immune system is supposed to develop by encountering microbes, so being too clean throws it out of whack as the immune system overreacts to minor insults.
Most of the research on the hygiene hypothesis has been more correlative than conclusively causal (or causally conclusive), but a new study, published in
Science—via Nature News—found
potential explanations.
The researchers induced two groups of mice — germ-free (GF) mice, which are raised in a sterile environment, and specific-pathogen-free mice raised under normal laboratory conditions — to develop forms of asthma or ulcerative colitis. GF mice had more iNKT cells in their lungs and developed more severe disease symptoms, indicating that exposure to microbes was somehow influencing iNKT cell levels and making the GF mice more susceptible to inflammatory diseases.
Furthermore:
The study also found that a lack of exposure in early life could not be compensated for by introducing the GF mice to a broader range of microbes in adulthood.
So basically there is a “launch window” in early life for exposure to these microbes.
The study is not without its limitations. First, mice are not humans (whence the question “are you a man or a mouse?”), and second, no human—not even Bubble Boy—could be kept as free from microorganisms as the mice that were used in the study. Still: “It supports the idea that the microbiome is very important and the age of exposure is decisive,” says Erika Von Mutius, head of the Asthma and Allergy Department at Munich University Children’s Hospital in Germany.
