In parts of the world, for example USA, Canada, Australia, Europe, other locations, serious parasitic infection are now not common. The immune system, which co-evolved with parasites over millions of years appears to turn on our own bodies because of the lack of parasites to attack. This hypothesis (the hygiene hypothesis) is investigated in the cited paper.
I referred to serious parasitic infections above because virtually everyone host some benign parasites such as the Demodex mite, a microscopic mite that lives on our eye lashes. See .
Finally, let me recommend Parasite Rex... by Carl Zimmer. 
The biggest metric I have for this is that when I am genuinely sick - with a cold or fever - it seems my body stops keeping things like HPV at bay and I start to see remnants of things like warts I haven’t seen for years start to pop up again - and of course disappear again along with the fever.
By that hypothesis, willingly introducing some (preferably benign) parasite or infection would keep it busy so it doesn't attack itself?
Just thinking out in text here, I'm tired heh
Edit: Oh, it’s already happening: https://news.ycombinator.com/item?id=25961202
Just imo, there's nothing wrong with experimenting on yourself, as long as you take the responsibility and accept the risk and possible consequences.
Hacking is not only for electromechanical things :)
Edit: I read a more recent article about the guy, and it said he subsequently backed off the idea after his allergies came back.
I get what you're saying, and I agree. I would waive health/social benefits if I were allowed to experiment stuff on myself. Zero liability for the state.
Of course, that's a move only for the desperate whom the system failed over and over again. At that point, why not?
Too many helminths seems to have deleterious effects, however, so there seems to be a balance that must be struck.
There is evidence that these worms affect the microbial mixture in the gut.
Generally speaking, modern humans live in sterile conditions whereas we have ferocious immune systems which evolved to handle filthy conditions. The theory is, given too little work to do, some people's immune systems start to attack the self.
Anecdotally, I have an incredibly healthy daughter; we never hesitated to expose her to as many strangers as possible. "Would you like to hold our baby?" She also got mother's milk for several years (advantage of being an only child). Almost never gets sick and when she does, it's for less than 24 hours. Hopefully it stays that way :)
Day care centres are what their immune system is designed to fight.
I’m not sure how old your daughter is, but I have never been sicker than the few years my child attended one. I work in a hospital and my wife is a teacher, so it’s not like we weren’t exposed to bugs.
No matter how clean the child care centre, kids are a Petrie dish of horrible diseases.
Then there’s sugar, processed food, work stress, particle emissions, microbes in indoor air... there are plenty of reasons for our immune system to attack itself.
A) it's extremely time-consuming and difficult to capture the mechanism for how organisms act in the middle of the human body in the middle of their lifecycle when we're not even sure what we're looking for, so it's just not been found yet.
B) it might just be safe and cost-effective enough to give people worms temporarily as a treatment instead for now. (I don't know if this is the case, but if they're doing it for a study, the risk profile can't be that bad...)
C) even if we isolate whatever mechanism they have (and can synthesize it readily), it's still an immune modulator, so all the same caveats for steroid creams might apply at any significant dose.
Sure, but it wouldn't be an infection you could spread to other people. It also wouldn't be an infection that could grow, of its own accord, to undesirable levels within you. That's a huge improvement.
However when crossing hosts signals can get crossed and they can cause serious health problems like eating your retina, brain, hearts, etc. Be very careful with parasites that aren't evolved for humans.
Necator Americanus was always specialized to infect humans. But it evolved to infect Africans, who brought it to the new world. For blacks, it doesn't pose much of a problem. For whites, it does.
If this became a routine treatment, it seems pretty likely that they'd start being able to survive.
For something to evolve like that you need to re-introduce the mutated strains back to the source.
If there is no re-introduction (which there wouldn't be, because the worms would be bred in an isolated environment and not the sewer system), then there isn't really anything to worry about. There is no selection pressure at the point where breeding and distribution occurs.
I imagine if such a thing did occur, they would just kill the batch they were breeding and start over from a known strain.
(Not a microbiologist, so who knows though)
Helminthic therapy is a real thing for people with severe autoimmune issues. There are folks in the US right now walking around with relatively mild hookworm infections and substantially fewer autoimmune symptoms :)
That said, Coronado Biosciences ran a pork hookworm clinical trial in the treatment of inflammatory bowel syndrome and it failed. More work needed.
This is just anecdotal (I know someone who did this and says that it worked) -- but please do your own research and consult a healthcare professional!!!
This is huge gross factor, but if it would give me a normal life I could tolerate it.
I remember pooping a really long worm some years ago, and taking a anti-worm medicine...
you can make a test at your gp
Exquisite election, nothing like a Lernaeolophus to appreciate our fine mammalian lifestyle. Nasty Necator, otherwise... yuck.
These definitions were pulled from https://www.merriam-webster.com/dictionary/inoculate
Unlike Gwern, I still haven't shared any of it because I couldn't get my grabby hands on any of the actually effective ones, not even some more effective reuptake inhibitors (like, come on, I'm not asking for much, shitty healthcare systems!).
Plus, I don't think anyone cares... but apparently some people do huh.
What happens to people with narrowed arteries?
It can be prevented by using shoes and not walking barefoot.
There are also other species that infect cats and dogs. In those cases what often happens when the larva encounters a human is that it can enter the skin but it can't travel further, so it only does that first part with the itching and drawing red "lines" under the skin.