every time the subject of the "hygiene hypothesis" comes up, people roll their eyes, so I just assumed it was a topic that was real; but for some reason people didn't want to discuss. Kind of like global climate change. I'm kind of perplexed why people with CFS aren't more interested, seeing as how it probably plays a big role in our disease.
The theory of the "hygiene hypothesis" states that the loss of contact with the normal range of microbes that you would find in a rural environment / farm is responsible for the apparent rise in allergies, autoimmune conditions, asthma, etc.
The hygiene hypothesis of allergies and autoimmunity posits that our much more sterile modern urban environments are cutting us off from beneficial bacteria that stabilize our immune systems and prevent allergies and autoimmunity.
I don't think the hygiene hypothesis is likely to be true, though there may be some truth to it. I can appreciate how the loss of beneficial gut bacteria and gut worms can ramp up allergies and autoimmunity (especially, worms which usually secrete anti-inflammatory factors in the gut — the basis of helminth therapy); but it is not clear that the rural lifestyle would automatically always provide you with beneficial gut organisms: after all, there may be just as many bad bacteria in the rural environment as good. How can you be sure that you only pick up the good microbes? You can't really.
I would suggest the reverse hypothesis: that the rise of allergies and autoimmunity in modern urban environments may in fact be more due to
urban microbial overload: that is to say, due to the very strong possibly that, in a modern urban environment, we are
far more exposed to microbes, not less.
This is because a large proportion of the microbes we catch are microbes that are transmitted human-to-human, and so the
vastly increased number of human beings we have daily contact with in urban environments provides much more opportunity for us to acquire pathogenic viruses, bacteria, etc from other people. Globalization makes this even worse, allowing microbes to easily colonize every corner of the planet.
For example, the respiratory virus I caught that led to my ME/CFS was picked up by kissing on a date with someone that recently arrived in my city. I developed a bad sore throat by the following morning, and then ME/CFS and other disorders were rapidly precipitated by this virus (and not only in me, but also in several others that unfortunately later caught the virus from me).
In summary: I suggest rural environments may have been healthier in terms of allergies and autoimmune conditions not so much because of the greater daily contact with a range of microbes that rural environments provide, but because rural environments are more remote, and so isolate and protect you from the large range of pathogenic viruses, bacteria, etc that are carried by the mass of humanity.
Incidentally, I just came across
this new study that, for the first time, throws light on the mechanism by which microbial infections can precipitate autoimmunity. I think this study may have significant implications for ME/CFS.