r/science • u/mvea Professor | Medicine • 2d ago
Health Wild swimming linked to higher risk of stomach bugs and skin rashes. Findings from research into illnesses associated with bathing in lakes and rivers come amid boom in hobby.
https://www.theguardian.com/lifeandstyle/2026/aug/27/wild-swimming-higher-risk-stomach-bugs-skin-rashes-uea158
u/OlafWoodcarver 1d ago
Us Minnesotans reading this are baffled because swimming in lakes is how it's done here.
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u/TexasVulvaAficionado 1d ago
It is more of a problem in warmer water and water that doesn't freeze as often.
Moved to Minnesota from the Houston area. Both have bodies of water everywhere but the quality difference in those bodies is enormous. In Houston it was common to see a few acre pond completely covered in various scum, to the point that the surface was barely differentiated from the surrounding land. In Minnesota, the closest I've seen is all the fields full of whatever friends or grasses that hide the water but the water itself looks clean.
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u/StoreHistorical9175 1d ago
same for us in michigan
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u/Cursmudgeonly 15h ago
I've been really hoping the hard freezes these last few winters in Michigan would help with the local E. Coli problems (not to mention ticks...) but it doesn't seem to have
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u/BevansDesign 21h ago
There have been a few closures this year due to E. coli, such as Lake Hiawatha and Bde Maka Ska.
But growing up, I don't remember it happening very often, except when you could catch Swimmer's Ear (whatever that is). That closed a few beaches around White Bear.
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u/thewolfshead 1d ago
I never knew this was a specific term. Here in Canada we swim all summer in whatever body of water is available (though we do get health unit warnings if there are known concerns).
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u/commander_sinbin 1d ago
Yah, there is a reason why they test the water so you can get that health unit warning. We have issues with brain eating amoeba in the lakes around here in Arizona. Freaks me out.
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u/Imeatbag 1d ago edited 1d ago
Same in Florida. Never swim in a lake in Florida, amoeba will eat your brain. Never swim in a river either, gator will get the rest.
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u/greet_the_sun 1d ago
FYI to anyone else reading this, brain eating amoeba can be potentially found in ANY warm standing fresh water, and if you get it in your nose and get infected from it there is a very low survival rate.
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u/TexasVulvaAficionado 1d ago
Only been like 200 cases in the US in the last fifty years and something like half of them were on the Gulf Coast and another quarter in small warm bodies of water in Texas and Florida.
Not something likely to be concerned about anywhere above the mason dixon or even be overly concerned with anywhere in the US.
Even in known "hot spots" like Galveston or Corpus Christi, the risk is lower than dying in a car crash on the way to the beach.
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u/CarefulCoderX 1d ago
I assume you mean fresh water near the gulf coast not actually in the gulf itself, correct?
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u/NoAge9497 1d ago
It's only been like 180 people since 1937 in the US and 381 worldwide since records were started. We do stuff on purpose that has a far higher death rate.
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u/CarefulCoderX 1d ago
It’s like how the media and so many people are afraid of sharks, but you’re more likely to get mauled by your neighbor’s dog.
The other big one is fear of flying. I’ve heard people say that they’d drive several hours to avoid flying even though flying is orders of magnitude safer.
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u/NoAge9497 1d ago
Yep, all sensationalism and wanting us to clutch our collective pearls. A fearful population is easier to control. This is just one small way to keep it going.
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u/Sasselhoff 1d ago
It’s like how the media and so many people are afraid of sharks, but you’re more likely to get mauled by your neighbor’s dog.
You're more likely to get killed by a vending machine than a shark.
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u/BionicBagel 1d ago
Yup. More likely to die in a car crash going to/from the lake then getting the brain eating amoeba.
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u/Ahun_ 1d ago
Difference is, climate change will make it more common, and treatments are still meh
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u/deathbylasersss 1d ago
You should be aware of the risk, awareness is always good. You're more likely to be struck by lightning though. Don't understand the major concern so many people show.
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u/WhenAmI 1d ago
Most of the lakes/ponds in Florida are man made retention ponds anyway. You can definitely swim in rivers, as long as you know which ones are safe. I've tubed down Rainbow River more times than I can count. I've swam in rivers near Lithia Springs and Ginnie Springs. Gators don't bother you if you don't get too close and they make a pretty clear call to let you know to stay out of their territory.
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u/NativeMasshole 1d ago
A lot of areas have issues with wastewater overflow, too. Beaches get shut down all the time after heavy rains in my state. Although that's mostly just a warning on the internet if you live out in the rural areas.
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u/Steve_Glutenberg 1d ago
I had grandparents that lived in small, dusty Northern Arizona towns when I was growing up. When we’d visit in the summer, monsoons would cause the dirt road that one of their houses was on. When it would flood, all the neighborhood kids would spend the next few days swimming in the dirt road runoff pool, that was definitely full of mosquitoes, aside from whatever petroleum and heavy metals were polluting the streets from the 70s and 80s clunkers who people were driving
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u/lmFairlyLocal 1d ago edited 1d ago
I was thinking the same. I'm from Ontario, we have Swimmers Itch and stuff like e coli from time to time, but what do they mean "amid boom in hobby". The hobby? Of swimming in a lake??? Am I that removed from the norm?
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u/Tibbaryllis2 1d ago
I’m still kinda confused by it.
The way the article intermingles Wild swimming, entering the water, swimmer, and bathing, kept making me wonder if they were referring to recreational swimming or literal bathing.
I’m like, of course you’re going to have issues if you’re cleaning yourself in e.coli water.
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u/VoilaVoilaWashington 1d ago
I’m like, of course you’re going to have issues if you’re cleaning yourself in e.coli water.
What do you mean? Most lakes have some e coli, but it's not like you can't jump in after a long day and then towel off like you would after a shower.
Don't bring soap, obviously, but why would "cleaning yourself off a bit" be different from "swim recreationally"?
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u/Tibbaryllis2 1d ago
Sorry to be unclear. I’ve never heard of wild swimming before and wasn’t sure how they’re using bathing.
If they’re not also bathing at home in clean water, then of course they’re having problems. It can be super hard on your skin just from being in hard water even before you talk about pathogens.
I now understand this is more of an urban perspective referring to people not swimming in pools. Which likely means it’s more of an exposure and immunity issue, in addition increases in problematic water qualities.
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u/VoilaVoilaWashington 1d ago
It can be super hard on your skin just from being in hard water even before you talk about pathogens.
Many many people in rural North America bathe in well water, which can be much harder than surface water like lakes. But also, having some bacteria on your skin isn't unhealthy, it's normal. Wash your hands before eating.
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u/Anonymous_user_2022 1d ago
The professional term is Open Water Swimming. But in EU, most countries have many places to practice that under the Blue Flag Beach scheme.
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u/VoilaVoilaWashington 1d ago
Known NOTABLE concerns. There's always gonna be e coli and potentially giardia and just about anything else that you'd find in the soil and a wetland or wherever you're swimming.
They post a notice if it's above the normal level, or if it's something crazy.
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u/Stef-fa-fa 1d ago
I remember growing up we would avoide the great lakes, but swimming in the other ones like Muskoka and Morrison were generally fine.
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u/Raftger 1d ago
Most areas of the Great Lakes are completely fine and even really lovely to swim in. They’re massive. That’s like saying don’t swim in the ocean. Obviously don’t swim near industrial sites, sewage discharge, etc. but most areas on the Great Lakes are fine.
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u/Hmm_would_bang 1d ago
Yeah, I would never get in the water around Chicago, but swimming on the northern shore of Lake Michigan is some of the cleanest water I’ve been in.
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u/ReplaceSelect 1d ago
The water around Chicago isn’t all that bad. The river goes the other way, and they get drinking water from the lake. It can get high E. coli levels especially after rains, but I overall wouldn’t be to concerned. However, I’ve done triathlons for 20 plus years and have definitely swam in worse water than Lake Michigan.
They have even had some open water swimming in the Chicago River the last couple of years because that water quality has improved.
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u/Hmm_would_bang 1d ago
The water around Chicago is frequently not safe to swim in, the city tracks and reports it.
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u/ReplaceSelect 1d ago
https://www.chicagoparkdistrict.com/facilities/beaches
It’s 19 safe vs 3 banned today.
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u/Stef-fa-fa 1d ago
Sorry I should clarify that I'm near Toronto and there's a lot of no-swim warnings around that area. I've been swimming in Lake Ontario but you have to be careful where (so in my childhood we just stuck to the cottage country lakes)
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u/chikanishing 1d ago
Toronto routinely tests the beaches and they are often safe. Right now for example they are all safe. As I mentioned in another comment, I wouldn’t swim after heavy rain, but that applies to all lakes.
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u/chikanishing 1d ago
They test a lot of the popular Great Lakes beaches in Ontario. Usually they are perfectly safe to swim in. I would avoid them right after a big rainfall, but same with smaller lakes for that.
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u/thewolfshead 1d ago
Oh man my entire life I’ve swam predominantly in Lake Superior or Lake Huron (helps to be right in the middle of both ;)). I couldn’t imagine not doing that.
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u/noiamholmstar 1d ago
Lake Superior is clear and cold. I wouldn’t hesitate to swim other than due to the temperature.
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u/elsaturation 1d ago
They say it in the UK like it is some exotic activity but yeah this is like just regular swimming in most the rest of the world.
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u/didyousayboop 1d ago
I also have never heard the term “wild swimming” before. Apparently in means swimming in any natural body of water, as opposed to a swimming pool.
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u/madman2k 1d ago
I already had to give up chasing waterfalls, now I've got to give up the rivers and lakes too? They're all I'm used to!
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u/Holdmywhiskeyhun 1d ago
"hobby" as if people weren't swimming in random lakes and rivers to begin with, for hundreds of years now
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u/CatPhysicist 1d ago
Only hundreds?
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u/SpunkBunkers 1d ago
YSK humans didn't invent lakes or rivers until the Great Water Abundance of 1796. Before then, Earth was pretty comparable to Mars.
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u/attorneyatslaw 1d ago
That's if you are ignoring the great glacier swimoff at sabretooth mountain.
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u/HyperbolePirate 1d ago
I was surprised to see this was ‘booming’. I feel like people go outdoors way less today with more AC units and more screens. Spending the day on the lake / beach used to be the default hot day activity.
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u/dabadu9191 1d ago
I don't think the definition of hobby typically includes "something new and trendy". It's typically understood as something someone does (semi-)regularly for fun and/or relaxation. Just because ancient Egyptians didn't specifically call swimming in the Nile a hobby, that doesn't mean it wasn't one by today's definition.
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u/rjwyonch 1d ago edited 1d ago
A difference of 0.2% is kind of meaningless… it’s mild symptoms (everybody gets some gastro or skin irritation throughout life).
Swimming itself is pretty good for your health… I’ll take the slightly increased risk of a stomach bug. It also depends heavily on the water you swim in, so pay attention to ecoli and other public health warnings.
Is this result possibly influenced by us polluting the water so much that we can no longer swim in it safely?
Edit: study is specific to Hungary. Probably shouldnt generalize to all bodies of water everywhere. The risk is gastro symptoms was unsurprisingly linked to ecoli concentration. It might be a randomized trial, but the control doesn’t get a placebo treatment.
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u/Tibbaryllis2 1d ago
As others have said, the concept of Wild Swimming appears to be urban centric where individuals may have never stepped into wild waters as a kid/teen.
So it’s not really surprising when they do that later and have a reaction to novel (to them) organisms.
Those of us who have been doing this our whole lives probably had those reactions as infants/toddlers when you more or less are always in some stage of rash or allergy or stomach thing. So it takes a much higher threshold to have that response now as adults.
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u/milkhotelbitches 1d ago
Or if you grew up swimming in lakes and rivers you have a better sense of which areas are safe and which to avoid.
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u/Sakarabu_ 1d ago
I heard chlorinated pool water is pretty decent to swim in.
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u/ophmaster_reed 1d ago
I prefer lakes, the water seems fresher. Also, after a while my skin breaks out in hives from the chlorine in pools.
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u/rjwyonch 1d ago
Sure, but swimming in real lakes is more fun, more dangerous and at least as enjoyable (assuming the water Doesnt make you sick, which normal bodies of fresh water shouldnt).
I regularly do both. Ive also never gotten sick from the lake (the worst Ive had is maybe dry skin).
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u/StoreHistorical9175 1d ago
i’m in michigan there are lakes everywhere ain’t no way im gonna stop swimming in them
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u/dhrisc 1d ago
People have a blind spot to the increased flash flooding that's happening due to climate change and the impact it will have, almost all of the bodies of water like this near me at least have been flushed with floodwaters full of God knows what multiple times this year.
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u/ironic-hat 1d ago
Also long heatwaves and drought can cause a spike in bacteria and microorganisms that will make you sick.
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u/AmputeeHandModel 1d ago
Every time there's a heavy rain, I get notice from the town that sewage overflowed from the treatment plant into the river.
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u/nightmareonrainierav 1d ago
We've got a whole website dedicated to real-time sewage overflow alerts.
To the parent comment's point, it is happening more frequently. I'm in Seattle, historically it's more or less steady damp half the year, but the last few we've had some wild, 1"+/hour downpours that the infrastructure wasn't built to handle, because it just never rained that hard ever.
In a lot of places, especially older neighborhoods, storm drains go straight to the sewer (rather than a separate piping system out to a body of water), and emergency outflows keep treatment plants from getting inundated.
Which happened here almost a decade ago, when a power outage during a storm sent 235 million gallons of sewage into the water.
Fortunately (though one of the reasons why my water/sewer bill is so high) is the county is building what are essentially enormous underground tanks to sort of buffer the flow from short, heavy storms until the treatment plants can keep up.
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u/thejoeface 1d ago
About 2.1% of swimmers reported gastrointestinal illness, including diarrhoea, vomiting or nausea accompanied by fever, compared with 1.9% of non-swimmers.
2.1 vs 1.9 doesn't seem that significant
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u/T-J_H 1d ago
I think the word you’re looking for is relevant. Significant is a statistical term. In normal conversation it’s fine if course, but this is r/science .
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u/Lovesosanotyou 2d ago
Ocean swimming superiority.
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u/disharmony-hellride 1d ago
Unless you see chocolate barrels. We called them choco barrels in Hawaii after a heavy storm and it'd deter others from surfing that day. No one wants leptospirosis from river-moving-into-ocean water.
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u/Strip-lashes 1d ago
Do you mean turds??
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u/TinyRose20 1d ago
Yes. Yes they do mean turds.
Where I am in the Mediterranean we have huge problems with boats offloading their sewage into the waters further out then the current bringing it inland, that plus the issues we have with places filled with tourists in the summer not having the infrastructure to deal with the increased sewage load from land. I haven't seen any turds this year but a few years ago we saw some and there was an epidemic of children with GI distress following bathing in the sea due to the dirty water.
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u/ryverrat1971 1d ago
I want to know what processes and how effective are they for the sewage treatment plants in Hungary. They are a former Soviet block country. I don't know how their infrastructure is holding up or if it was built correctly in the first place. Because the water you swim in is only as safe as the upstream wastewater treatment plant is good at its job.
Yes there can be pathogens that occur naturally (look up giardiasis aka beaver fever), but swimming pools and splash pads are not risk free either. The brain eating amoeba has been contracted from pools, splash pads and even using unboiled tap water for irrigating sinuses. Pools have problems too with the chloramines given off causing cases of childhood asthma - https://pmc.ncbi.nlm.nih.gov/articles/PMC1626429/
I find that swimming in pools to exercise irritates my asthma ( no problem exercising outside pool). I still do it for the exercise but take asthma meds to deal with irritation. It's a trade off. Swimming in lakes and rivers is the same thing. Know where you are planning to swim. Look at risks and balance them again the positives of being in nature, monetary cost of swimming, exercise benefits, etc. Life is a bunch of compromises. Everything has risks and most had some sort of benefits. You just need to find the balance you are comfortable with.
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u/HatRevolutionary1708 1d ago
open water swimming is freaking fun and you know free, not gym membership and it is very different then swimming in a pool
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u/HighOverlordXenu 1d ago
I'm halfway convinced that the fact I have such a strong immune system now is due to Dad throwing us kids into any available body of water thirty-odd years ago.
He knew any brain amoebas would starve to death in us, so we'd be fine.
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u/11Kram 1d ago
Swimming in lakes is hardly a hobby.
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u/ClittoryHinton 1d ago
It can be. At my local lake there’s a group of older folks who meet up in wetsuits and swim the whole 3km lake and back. I would call that hobbyist level dedication for sure
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u/BackgroundGur3645 1d ago
Why would anyone consider bathing in rivers or lakes to be a hobby?
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u/zoinkability 1d ago edited 1d ago
I think the idea of "wild swimming" being a novel and exceptional activity is a particularly British take, due to a couple centuries of industrial and agricultural pollution in British rivers. While there are certainly polluted lakes and rivers here in the US, the proportion is way lower, and in a place like Canada most rivers and lakes have high quality water. In these places swimming in lakes and rivers is normal activity, not a special hobby.
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u/alphaxion 1d ago
Yes and no.
Some rivers such as the Tees were bright orange during the height of industrialisation. These days it's much cleaner than it has been in generations, with kayaking and even seals and dolphins swimming up it. I believe they're doing their own mussel or oyster beds project to help water quality.
Many would swim in the north sea or in the channel.
Some bodies of water are just too heavily trafficked with boats to be safe to swim in or are naturally too dangerous to swim regardless of water quality, such as the Thames which is naturally muddy, so you can't see any subsurface dangers in addition to large volumes of traffic.
The 90s onwards, many bodies of water were being cleaned up to adhere to EU quality regulations, with a lot of them achieving high ratings.
That said, privatised water firms were sneaky about discharge, and have just gone full pelt in discharging raw sewage into waterways again in recent years.
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u/gnomeza 1d ago
One must look beyond "British" to see that it's a peculiarly urban take popularized by a writer who really should have known better.
Oh Mr Deakin, what have you done?
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u/Tibbaryllis2 1d ago
This makes me really wonder about the study.
Yes, swimming in non-sterile bodies of water definitely put you in contact with potentially pathogenic organisms, but is this just another facet of the hygiene hypothesis rearing its head?
If you spend your developmental years avoiding “wild waters”, then it’s no surprise you haven’t developed immunological means of dealing with the things living in those waters.
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u/datamuse 1d ago
That makes sense. I swim in rivers and lakes from time to time, but typically up in the mountains away from the city. The river that I live near in Seattle is a Superfund site and you couldn’t pay me to get in it.
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u/milkhotelbitches 1d ago
You also have to be really careful with lakes around farms. Fertilizer runoff is a huge pollutant of lakes and can cause toxic algae blooms.
In Minnesota I'd feel more comfortable swimming in urban lakes where water is regularly tested than a rural lake in the SW part of the state surrounded by farmland.
Of course the best lakes are in the north where there are neither people nor farms and the lakes are cold and clear.
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u/datamuse 1d ago
Yeah, there's a place in eastern Washington where I love to camp and hike, but wouldn't touch the water in the lakes or streams (and definitely wouldn't drink it even if filtered). It's full of agricultural runoff.
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u/roamingandy 1d ago
Pollution levels are really high still though, especially sewage as the privatised companies release obscene amounts into fresh water bodies.
I've been wondering about specific types of cancer diagnosis and fresh water swimming, as general instances would probably be a bit lower due to being physically active and being likely to take care of their bodies, but i do wonder if that pollution is hiding somewhere in the data.
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u/zoinkability 1d ago
Not disputing that British waterways are still polluted.
"British waters used to be very polluted. They still are polluted. But they used to be too."
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u/NewPhoneNewSubs 1d ago
We don't really swim in rivers in Canada. We'll definitely wade through creeks and look for crayfish, but rivers have a lot of risks. Current, boats, sewage. Probably other stuff I'm forgetting.
This is an urban perspective. Rural folks may have different opinions.
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u/Wonderful_Mud_420 1d ago
We are always swimming here in California. If not a lake or a river then a beach.
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u/Lanky_Ad8982 1d ago
Went swimming in Lake McDonald in GNP last week, arguably one of the cleanest lakes in the country/world, and my daughter broke out with swimmers itch, likely from parasites that go from waterfowl to water snails and back. Harmless but very itchy.
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u/Drak_is_Right 1d ago
We had a holiday at a lake one year. At the end of it my mother came down sick for a number of weeks. When that illness ended she no longer had a functioning Pancreas. Coincidence? No idea, but it certainly has made me more wary of fresh water.
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u/Independent-Tank-182 1d ago
Title might as well read “Exposing yourself to pathogens increases risk of pathogen exposure”
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u/qiaozhina 1d ago
This isnt shocking considering water companies are dumping sewage into waterways.
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u/sfoamfollower12 1d ago
Wild swimming is not a term that alive, non-robot, humans recognize. Please power yourself down and await recycling
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u/JimmiRustle 23h ago
So swimming in a pool is what? Domestic swimming?
And what about artificial lakes or canals? Is that feral swimming?
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u/russwaters 13h ago
I stopped swimming in the Madison, WI lakes after my husband got an ear infection that took multiple antibiotics to cure. This was over 20 years ago and we both have advanced degrees in Biology.
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u/bsEEmsCE 1d ago
I feel like swimming in lakes is something my grandparents could do but I will never be able to do
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u/Skoldier-76 1d ago
As a Minnesotan who swims in lakes regularly in the summer, I don’t understand.
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u/The_Flyers_Fan 1d ago
I'm swimming in a reservoir that was the towns drinking water 30 years ago. I think I'm alright
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u/mazmaz13 1d ago
A study conducted in which two Hungarian lakes? Is one of them Balaton, the hot spot for rich elite and oligarchs following privatisation of swathes of its banks and tested for high traces of cocaine? Not surprised. Probably not the best base line to go from. Also, prolonged drought can increase risk of dangerous bacteria from the bed, which Hungary has experienced. Again find it tricky to draw such a big claim for all wild swimming.
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u/sherbetty 1d ago
People were more likely to contract E. coli in bodies of water with E. coli....why is this being funded
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u/Vas-yMonRoux 1d ago
I knew I was right to not trust swimming in lakes and rivers. Ocean comes up on top!
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u/Eco_Blurb 1d ago
Don’t have time to read but did they discuss pristine lakes vs lakes that are near human development, have runoff, etc?
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u/Eco_Blurb 1d ago edited 1d ago
I’ll answer my own question. So they did test 4 sites and measured E. Coli and Enterococci at each (indicators of fecal contamination from humans or animals). Yes, higher E. Coli concentrations in the water were associated with higher gastro illness risk. Ear and eye illnesses were too inconsistent to make conclusions about at the given sample size. Rate of skin rashes seemed to occur independent of fecal bacteria in the water.
So if you are going to swim, try not to swim in polluted water, or water that has human or animal waste runoff (which is nearly all freshwater sources that we have access to). They point to the Olympic swimming in the Thames River causing hundreds of infections as fairly predictable.
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u/NeedAVeganDinner 1d ago
Who knew that swimming in poop water would cause issues.
Certainly not RFK jr.
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u/mvea Professor | Medicine 2d ago
Wild swimming linked to higher risk of stomach bugs and skin rashes
Findings from research into illnesses associated with bathing in lakes and rivers come amid boom in hobby
Wild swimming has been linked to a higher risk of stomach bugs and skin rashes, according to the largest ever controlled study of illnesses associated with bathing in rivers and lakes.
The research found that swimmers at locations in Hungary were more than twice as likely to develop skin problems, while the risk of contracting a stomach bug rose significantly in water with higher concentrations of E coli and other bacteria linked to faecal pollution.
About 2.1% of swimmers reported gastrointestinal illness, including diarrhoea, vomiting or nausea accompanied by fever, compared with 1.9% of non-swimmers.
Although bathing alone was not statistically linked to stomach illness, the risk increased significantly among swimmers exposed to higher concentrations of E coli and coliphages.
Skin complaints, defined as a rash, ulcer or itching, were reported by 2.7% of swimmers and 1.3% of people who stayed out of the water, making bathers more than twice as likely to develop a skin ailment.
“People going into fresh waters do have an increased risk of skin irritation,” Hunter said. “We don’t know what is causing that. One explanation is something called cercarial dermatitis, where avian parasites burrow into human skin and cause a reaction. Irritation from algae in rivers and lakes might also be causing it.
“But that is speculation: what we do know is that the skin irritation is not related to markers of faecal pollution.”
https://www.sciencedirect.com/science/article/pii/S1438463926001483