HORMESIS.

I had originally flagged "Playing in mud and dirt can boost your child's immune system" as a Friday short take, until that post began taking on the form of a Chicago Great Western freight train and a passage from War of the Worlds came to mind.

These germs of disease have taken toll of humanity since the beginning of things — taken toll of our prehuman ancestors since life began here.  But by virtue of this natural selection of our kind we have developed resisting power; to no germs do we succumb without a struggle, and to many — those that cause putrefaction in dead matter, for instance — our living frames are altogether immune.

But our "microscopic allies" must learn, one child at a time.

My deeper fear, though, is that it's likely to be something as small as bubble-wrapping our kids that will turn out badly.  Note how quickly peanut allergies and chemical sensitivities have emerged, particularly among the spawn of the well-to-do?  I wonder if Mr Limbaugh has ever heard of hormesis. (He has heard about the return of leprosy, which is something I though had been consigned to the Parables, and he has urged Our President to point out that California cities are "Detroit and Baltimore with palm trees.") Reflect, also, on how in several centuries of vaccination, that part of the population with immune systems less robust against the various contagious diseases has benefited relative to their neighbors with more robust immune systems.  I hate to contemplate an outbreak of smallpox or measles or any antibiotic-resistant bacteria.

I wrote that post in September of 2019, when only a few people outside the National Institutes of Health could find Wuhan on a map, and there's nothing in the early returns on the effectiveness of the rapidly developed coronavirus vaccines that calls into question that "robust against" passage.

The article on making mud pies reinforces everything Mr Wells wrote and I conjectured.

Evidence suggests that exposure to the microbes in dirt might actually help children develop stronger immune systems—and may even decrease their risk of developing allergies and autoimmune diseases.

Mud is not just a mix of soil and water. It's a complex ecosystem filled with microorganisms. One gram of soil can harbor up to 10 billion microorganisms—of potentially thousands of different species.

The diverse array of bacteria, fungi and other microbes present in mud and soil play a crucial role in our health and is key to what immunologists call "immune training". This is the process by which the immune system learns to distinguish between harmful pathogens and benign environmental substances.

During childhood, the immune system is especially adaptable. When exposed to a wide variety of microbes, it learns to strike a balance—responding aggressively to harmful invaders while leaving harmless substances, such as pollen or food particles, alone.

That's why we speak of "childhood diseases."  Those adaptable immune systems get stronger knocking down measles or mumps in youngsters, protecting the adult from the more serious consequences that can follow measles or mumps in an adult.  Wise parents will get their kids immunized against those diseases all the same.  But a little play making mud pies or petting the dog is beneficial.

According to the "hygiene hypothesis," as societies become more urbanized and sanitized, our immune systems are deprived of the microbial challenges they need to develop properly. This may cause the immune system to become hypersensitive, mistaking innocuous substances—such as pollen or dust—for dangerous invaders. This hypersensitivity can manifest as allergic conditions such as asthma, eczema or hay fever.

Lack of microbial exposure, particularly in early childhood, may also increase the likelihood of developing common colds and other childhood illnesses due to the immune system not being properly trained to handle everyday pathogens.

The lack of such immune training could potentially explain why children growing up in sanitized environments (such as cities with limited exposure to animals or nature) are up to 50% more likely to develop conditions such as asthma and food allergies. Their immune systems, unchallenged by natural microbial exposure, may overreact to harmless triggers.

Furthermore, without regular microbial interactions, the immune system may turn on the body itself—potentially contributing to the development of autoimmune conditions such as type 1 diabetes or multiple sclerosis. Research even shows that children raised in environments with high levels of microbial exposure—such as farms or homes with pets—are less likely to develop allergies or autoimmune diseases.

That "sanitized environments" include "cities with limited exposure to animals" offers one possible explanation for multiple sclerosis not being known as a specific affliction until sometime around 1860.  That a little playground play or a few interactions with local dogs might protect youngsters against asthma, lupus, or even diabetes is intriguing.  Maybe a little sugar, chocolate, and peanut butter with the baby food to pre-empt those food allergies?

There's no end of interesting research questions, is there, dear reader?  Kindly be advised that washing your hands before you eat or after you've answered the call of nature or interacted with that dog remains your sacred duty.