If your doctor told you that you were infected with worms,
your first question would probably be,
“How quickly can I get rid those worms in me?”
And I get that.
I mean, look,
you don’t want worms wriggling around inside your intestines.
It’s enough to gross anybody out.
But what if I told you
that you might want to have parasitic worms inside you?
Because some doctors have actually found a connection
between having worms and not having
immune system problems like allergies or arthritis.
The idea is that these worms have set up shop
in our bodies for so long.
that our immune systems might have
gotten used to them.
To the point that being worm-free
can actually cause its own issues.
It’s part of the hygiene hypothesis,
which was proposed by epidemiologists
back in the 1980s to explain why
allergies and autoimmune conditions like asthma are
so much more common today than they used to be.
According to the hypothesis,
people’s immune systems might be out of whack
because we’re too clean.
Filtered water didn’t exist for an awful long time,
let alone hand sanitizer stations.
So for much of our evolutionary history,
everyone was constantly exposed to things
like bacteria and parasites.
It’s your immune system’s job to keep these things
from settling in and harming you when they get inside.
So when it finds something foreign,
it defends your body by triggering inflammation
这表现为发热 发红 肿痛
that hot, red, swollen achiness.
Those symptoms happen because the area is flooded
with an army of white blood cells.
The compounds they release either attack the foreign material,
or call in reinforcements.
But the compounds that do the bulk
of the attack don’t just target invaders.
They can harm your own cells, too,
and your body can get caught in the crossfire,
which causes damage and pain.
Allergies, for example, are a special case of inflammation,
where the body is overreacting
to something that’s usually harmless, like pollen or dust.
And autoimmune disorders come from parts
of your own body triggering inflammation.
Like rheumatoid arthritis,
where joints basically become
permanently inflamed, or multiple sclerosis,
where the immune system attacks the protective coating around nerves,
and sometimes the nerves themselves.
All these conditions are becoming more common these days,
especially in wealthy nations
where you would think easy access
to high-quality medical care would prevent them.
而这就是产生寄生虫 即蠕虫 的地方
That’s where parasitic worms, collectively known as helminths, come in.
The group includes things
如绦虫 线虫 吸虫
like tapeworms, nematodes, and flukes,
which steal nutrients to survive.
Most get cozy in another animal’s intestines or blood.
Some species cause pretty severe symptoms
like the worms behind schistosomiasis,
他们会导致贫血 肝脏衰竭 膀胱癌
which can cause anemia, liver failure, bladder cancer,
or other awful conditions.
But many others don’t.
Like, if you had a tapeworm right now,
you might have no idea,
which is a super creepy thought, actually.
For those more benign species,
the fallout that can come from launching your immune system nukes at them
can be worse than the damage from the worms themselves,
which is why some epidemiologists think
that our immune systems have evolved to function
with certain parasites, to some extent.
That might sound kind of backwards,
but studies have found that rates of asthma and allergies
are higher in places with fewer parasite infections,
like those with more sanitation and access to healthcare.
And even though treatment is obviously worth it
when the worms are causing health problems.
Other research has suggested
that getting rid of parasites can have unintended side effects.
For instance, in a 2006 study,
ridding 317 children from Gabon of their intestinal parasites
made some of them have an allergic reaction to mites.
Similarly, a 2011 study looked at more than 2500 Ugandan women,
some of whom were treated
with deworming meds while they were pregnant.
While the treatment helped prevent
potentially serious complications in both adults and babies,
it increased the likelihood
that the kids would have eczema or wheezing,
both symptoms of allergic responses.
And a small study of 12 multiple sclerosis patients
found that those with worms
had less nerve damage over time.
But when 4 of them were treated, their multiple sclerosis symptoms got worse.
It seems strange that having a parasite infection
could keep you healthier in these specific ways.
So to figure out why this pattern exists,
immunologists have looked at how our bodies
respond to helminth infections.
They’ve found that some parasitic worms seem
to make our immune systems kind of hold back
by releasing anti-inflammatory signals that make it
so our bodies don’t go overboard
trying to kill the parasites.
At the same time,
they’re also reducing the inflammation that leads to
autoimmune conditions, and the overreaction to allergens.
Helminths could also spur the production of regulatory T cells,
which recognize parts of your body
that might trigger inflammation and turn down the response.
These cells normally keep your immune system
from staying in attack mode
after the invaders are already dead
or from freaking out in response to harmless stuff like pollen.
And this was seen in those 12 multiple sclerosis patients
those with parasites had more regulatory T cells
recognizing a protein that triggers the attack of neural tissue,
which could be why they had less nerve damage.
Doctors are trying to figure out what it is
about the worms that triggers these regulatory mechanisms.
That way, they might be able to
turn the compounds involved into treatments
for all kinds of autoimmune diseases.
It would be all the benefits of worms, without all the worms!
To be clear, we here at SciShow do not recommend
infecting yourself with worms to try like,
cure your tree nut allergy.
Unless your doctor prescribes them,
which is kind of possible.
Some doctors are putting the hygiene hypothesis
to the ultimate medical test: clinical trials.
Most of these trials are still in the early stages,
and results are mixed.
But some researchers remain hopeful.
We already know that our health depends on
tons of other organisms that live on and in our bodies.
So maybe parasitic worms are just part of that.
Just a lot bigger.
But again, we are not recommending
that you stop washing your hands
or, like, walk around barefoot around a lot of human feces.
Don’t do that.
If you want to learn more
about your health and medicine and healthcare policy,
you can dive even deeper
by checking out our sister channel Healthcare Triage hosted
by Dr. Aaron Carroll over at youtube.com/healthcaretriage.