You want to know a secret? An overlooked cause of chronic immune system activation?
It's right there on your plate: Nutrition.
Forget about "gut flora disbalance" or somesuch BS. Forget about makebelieve "latent viruses" supposedly hiding somewhere in the tissue (hiding like commies during McCarthy's withhunt). If you want to know what has the potential to activate the immune system, you should look on your plate.
For decades I had acne (and other inflammation of the skin) and it only receded when I reduced dairy. When I increased dairy again, the acne came back. Over the past year I had to learn that acne can be caused by other (ruminant) animal products like veal, lamb or sheep.
Got milk? Maybe that's the reason you got an activated immune system.
Connecting gut problems with nutrition should be easy, one thinks. So if one has known gut problems, why not think about nutritional causes? And from my experience, I can say that skin tissue (and oral mucosa) can be affected by nutrition – and the skin is probably (considering the path nutrients take through the bloodstream) the furthest away from the gut*. So it is only a small leap to consider that
every tissue between the gut and the skin can be affected negatively by nutrition. Right?
There is only one way to find out: Do an elimination diet. (Almost) no doctor will help you that, no "multi-center microbiology deep-sequencing study" will help you with that, and certainly no virus-hunter (real or imaginary) will help you with that.
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* Unless of course you consider that mathematically the
gut wall and the skin are part of the same surface. And that
evolutionary the different epithelial tissues might be very closely related anyway.