We have been learning more and more about the importance of the gut microbiome, from emotions and intelligence to immune responses and hormones. It is my opinion that children should be allowed to explore and "get dirty" so to speak. It would train and expose their body to different elements and pathogens that build a balance and "natural" microflora. By babying and obsessed with keeping kids clean and spotless all the time, we may actually hurt them more in the long run.

A bit of dirt, some sneezes, a scratched knee, a few bruises, all of them are normal and expected. Kids should be allowed to have those, otherwise we might deprive them of a healthy life later on.

Anecdotally, I grew up in a not so clean place. Thinking back, I am surprised it was so normal back then with how unhygienic everything was by Western standards. You would think people living in that kind of environment would be sick and disease ridden all the time. Yet it was the opposite. Allergies were practically unheard of and stuff like a cold or flu were almost never severe enough to send anyone to the hospital. Basically, people I knew back then were a lot more robust and had less health concerns than most of my coworkers and neighbors nowadays despite a world of differences in hygiene standards.

IIRC, germ free rodents grown to be absolutely sterile for specific medical tests are extremely sick all the time and are so weak you would not believe they are genetically the same with those rats thriving in the sewer. I guess it is for the same reason.

Tangentially it's not the main subject of the book, but in Burn by Herman Pontzner he discusses how the human body burns a set number of calories as measured by double labelled water studies and he speculated that the immune system goes into overdrive in sedentary individuals since we eat a certain amount each day and the immune system will be more active since they have excess calories to burn. In a South American hunter gatherer society they found they had so many infections that they speculated that immune system activity was using a significant percentage of their daily energy. There was an African hunter gatherer studied that did not have the issue with infections but were more active daily.
Whatever the tipping point is, it must not be that far off from how much you eat to be satiated in general. Go running or work out and its hard not to feel hungry later, unless you drink a protein shake or eat bigger meals that day.

> Intervention daycares received segments of forest floor, sod, planters for growing annuals, and peat blocks for climbing and digging.

They covered the backyars with forest elements, and asked the children to play with it.

> The 28-day-long intervention that included enrichment of daycare center yards for microbial biodiversity was associated with changes in the skin and gut microbiota of children, which, in turn, were related to changes in plasma cytokine levels and Treg cell frequencies. These findings suggest that the exposure to environmental microbial diversity can change the microbiome and modulate the function of the immune system in children. Specifically, the intervention was associated with a shift toward a higher ratio between plasma cytokine IL-10 and IL-17A levels and a positive association between Gammaproteobacterial diversity and Treg cell frequencies in blood, suggesting that the intervention may have stimulated immunoregulatory pathways.

Doesn't this just say that being exposed to more, and perhaps different, microbials will trigger your immune system? There are lots of words, but my casual eyes don't read anything that would be non-obvious. Specifically, nothing in this study seems to look at long-term effects. It was a 28 day study without later follow-up. Is there a well-established link between what they showed and lasting immune system changes?

(Making the headline _technically_ true.)

A lot of studies are like this. They build on existing ideas and push the boundaries in a very specific direction. Here they show that adding a forest floor environment to a kindergarten will increase certain immune related markers in the blood of the children playing there. They managed to design the study so that you can’t say “oh, but children playing in kindergartens close to forests probably don’t live in cities, so they probably don’t get exposed to as much pollution”.

Other studies will find links between those immune related markers and the development of autoimmune related disease, or someone will do a statistical analysis on kids that grew up in kindergartens close to forests to see if their incidence of autoimmune related disease is lower.

Humans and their lives are outrageously multi-faceted and thus nearly impervious to statistical analysis
By definition isn't that the case with everything in an uncontrolled system?
> Doesn't this just say that being exposed to more, and perhaps different, microbials will trigger your immune system? There are lots of words, but my casual eyes don't read anything that would be non-obvious.

There are many studies which evaluate things that seem obvious. These are necessary to support less obvious conclusions in other studies. If your paper is going to make the claim that IL10 upregulation in children as a consequence of environmental stimuli is linked to some disease process, one of the critiques will be if you can even establish that IL10 upregulation reliably occurs. If your paper can cite a well-performed study evaluating that prior, it strengthens the conclusions of your own study.

Makes total sense in hindsight, here's hoping this gets confirmed. It's also just generally a good way for young kids to develop. Kids learn a ton by figuring out "can I climb this log?"
Makes a lot of sense. I’m glad I grew up with dogs - they surely exposed me to all sorts of things as a child that helped build my immune system. Single data point, but I’m allergy free, no asthma etc.
I grew up in a super "dirty" household. Shoes in the house, dog, no house cleaners, the whole family did our own gardening and lawn care, etc. No allergies. In fact allergies were practically unheard of in that place and time.
I did too, but have allergies.

Maybe single data points aren't useful for the discussion.

> Shoes in the house, dog, no house cleaners, the whole family did our own gardening and lawn care

That's just a normal upbringing.

I grew up in a clean household, no shoes indoors, fastidious mother wiping down every surface, also allergy free.

So are all of my siblings though, so there might be more of a genetic component to this.

I grew up on almost a farm smack next to a nature park, was very outdoorsy kid and have all kinds of allergies ever since puberty onset.
Yeah I don't think allergies depend on external factors that much. My mother and I have pretty equivalent childhoods even down to same locations and she's wrecked with allergies and I have none, yet my health is worse overall (despite me having a healthier lifestyle).

While I believe some exposure helps build resistance ultimately your overall health will be influenced by stuff beyond your control AND your lifestyle/activities combined.

What? Shoes in the house is a bad thing? Isn't it worse to go with no shoes because you are adding sweat and maybe fungi to the mix?

I always lived in very clean houses and no one of us ever went barefoot. (We did change shoes for slippers or equivalent rather quickly though).

Anecdotally having lived in both types of houses, sweeping and mopping is much more frequent in the house that allows shoes inside.
Dose creates a poison - Paracelsus (translated from Polish). I mean if someone is allergic on dogs it will probably not heal them from allergy. However I myself had allergy on dog's and cat's fur, but for some reason my parents bought me a dog, and I guess it was not the hardest allergy, because I grew up with it and now I have no allergies on dog's fur...
Growing up on a farm improves the immunological responses that regulates allergies, autoimmune and inflammatory diseases. Although it isn't exactly clear what causes it:

> The researchers suggest additional work is required to determine the extent to which other farm-associated factors, such as social and maternal interactions, aerial contaminants, antigens from bedding and early nutrition, contributed to the impact of the environment on increased local and systemic immune regulation. [0]

[0]: https://www.sciencedaily.com/releases/2012/02/120208132549.h...

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I'm trying to imagine how their reference point - "standard yard" - looks like. Do they mean a field of just trimmed grass and nothing else?

My daughter's daycare has trees, shrubs, flowers etc. with birds, insects and whatnot. People still get allergies (even to nuts, which was unheard of 30 years ago).

I mean, this study is useful and I can't imagine letting kids out to play in a boring landscape, but I wouldn't hold out hope for this being a significant factor in the development of allergies.

Significantly better than a monoculture society
Skogsmulle (forest school) FTW.
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