Grime Can Be Good For You?

In contradiction to what your mom and grandmother and untold others told you as a child, playing in the dirt and not scrubbing every last drop of grime out of your hands may make you healthier. As NPR’s Shots blog says, it’s been known for some time that “people who grow up on farms are less likely to have ailments related to the immune system than people who grow up in cities” — less likely, that is, to have ailments including asthma, allergies, inflammatory bowel disease and multiple sclerosis. Scientists have now found more evidence for the “hygiene hypothesis,” according to which those exposed in early life to more microbes — from other children, from animals — end up with immune systems that are better able to tolerate the irritants that cause asthma and are, therefore, healthier in the long run.

Microbes in the Gut Can Be Good

A just-published study in Science has found that, when one has microbes in one’s gut in the early stages of life, a certain, rare part of the immune system – invariant natural killer T cells (iNKT) — are in retreat. Without the microbes, “the immune cells go crazy in the lungs and intestines [the colon, in particular], increasing the risk of asthma and colitis,” as NPR puts it.

Richard Blumberg, the chief of gastroenterology at Brigham and Woman’s Hospital in Boston, and other scientists made these findings about microbes and immune cells in mice who were raised in entirely germ-free environments in a lab. The researchers were intrigued to discover that “the immune response in the super-clean mouse innards looked very similar to what happens in diseases like asthma.” So, as NPR continues, the scientists exposed pregnant germ-free mice to microbes the day before they gave birth. The baby mice were found to have fewer iNKT cells in their guts in their early life.

The iNKT cells seem to be crucial to understanding the mice’s immune responses: Genetically altered mice who were reared in a germ-free environment still do not get colitis.

Study co-author Dennis Kasper, director of the Channing Laboratory at Brigham and Women’s Hospital, says that scientists now have to pinpoint which microbes out of the 500 to 1,000 species in the intestine control immune cells.

What This Study Tells Us About the Hygiene Hypothesis

As humans are not mice, the study’s results may only extend so far. But Blumberg’s and Kasper’s research certainly lends weight to the hygiene hypothesis and could contribute to recommendations about the early years of child rearing. Other studies, notes NPR, have connected antibiotic use early in life to immune-based problems like asthma and food allergies; there is also “even some evidence that women might have more autoimmune diseases than men because they’re kept cleaner than boys as children.” Also intriguing is that such auto-immune diseases are more common in people in developed countries, and in those who move to these from developing regions.

Certainly the news that exposure to some microbes in early childhood might be helpful — beneficial — for lifelong health would have an effect on the industry that has grown around children’s health, all those anti-bacterial soaps and products and even the banishment of sandboxes from playgrounds. Far from being “next to godliness,” cleanliness might only be a harbinger of an asthmatic, food-allergenic individual.

Do you think the hygiene hypothesis is accurate?

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Photo by meeshypants


colleen p.
colleen p5 years ago

lucky you didn't get toxoplasmosis from the cat crap you ate.

Cindy B.
Cindy B5 years ago

I was raised in a vet clinic and boarding kennel, out in a farming community.. I was surrounded by dirt, weeds, all kinds of crops, all kinds of animals, all kinds of pee, crap, rotting stuff, and anything else you can think of.

My sister and I ate mudpies we made in the irrigation ditches. I (supposedly) ate cat crap out of the litter box and such things. We both played in the alfalfa fields all day and rolled around on the roads after dark (the asphalt still warm from the sun), and we only had to take a bath on Sat. night if we were REALLY dirty. I was a filthy little heathen my entire childhood, and I still am quite happy being dirty. I've never used hand-sanitizer or even washed my hands very often. I pick things up off the floor and eat them. I lick walls, rocks, and countertops... All fairly absent-mindedly; I just never actually think about germs!
And I really never get sick, have almost never had a doctor or health insurance. I'm my own doc. If I get injured I just leave it alone and heal really fast (I've had LOTS of sports injuries); and everybody thinks I'm at least 20 years younger than I am. PS, also "extreme ski" at 60 . Not bad for someone who, if you listen to the germophobes, shoulda been dead long ago.

Inga S.
Inga S5 years ago

Grandpa always said " A little bit of dirt just makes you grow better".

Sherrie Brunell
Sherrie Brunell5 years ago

I have Crohn's - a form of inflammatory bowel disease - and my mother, bless her heart, was a fanatical cleaner. She used to re-arrange the furniture on a montly basis, just to make sure she could get to every corner and crevice to make sure it was clean. (I don't blame her for my disease. There are other factors involved, and my mother is the best mom ever.)

For people like me, data supporting the hygiene hypothesis could point to a potential treatment. I'm trying to get into a clinical trial that will use sterilized whipworm eggs. The idea is that if you give your immune system something else to do (other than destroying your own intestines), it will provide for remission from the disease. There have been good results in Europe and I am hopeful as all other meds I have used only seem to work for a short while.

Laurie D.
Laurie D5 years ago

We just went too far after whole groups (villages and towns) of people died from contamination. Some where along the line we just need to ease up on the super clean! I guess it's personal opinion as to how much dirt to allow back into your life -- and your childrens' lives. Perhaps there should be a study to say WHAT is okay and what isn't.

Pamela K.
Pamela K5 years ago

The old adage : "You have to eat a ton of dirt before you die." seems to still be true. I practice "resonable" cleanliness but I don't obsess about it. My house is tolerable but not spick and span (don't look too closely in the corners) and I have dogs and cats that go outside and in and sleep in my bed. I routinely graze on veggies straight from the garden (but those from the supermarket are always washed first!).
I rarely get sick and have minimal allergies. Perhhaps it is just coincidence--but maybe not--the rest of my family (living elsewhere and being more anal about cleanliness) are plagued by allergies and the usual bugs that go around, despite multiple supplements and vitamins !

Donna Hamilton
Donna Hamilton5 years ago

There may be something to this theory. I was an unusually clean child, just couldn't bear to be dirty (even in my high chair, before I could speak, I would hold my hands splayed out away from me if they got any food on them, and wouldn't stop until my mother cleaned them); as an adult I don't have the best immune system and seem to catch everything going. Oh well, damage is done now, so I'll stick to being a clean freak!

iii q.
g d c5 years ago

not surprising...

Karen Garnett
karen Garnett5 years ago

This theory has been around for years. I totally agree with it. Unfortunately, we are becoming such a sterile people, that our immune systems do not have the opportunity to build themselves up.

Patrick F.
Patrick f5 years ago

Let your kids eat dirt, grime is good for building up the immune system. We are becoming more susceptible to germs because we have to have everything sanitized before we touch it. Feel free to swap spit too,lol