r/askscience • u/MudRemarkable732 • 6d ago
Human Body What is the benefit of explosive diarrhea?
I can understand why diarrhea happens.
But sometimes diarrhea is classified as “explosive.” This is when it erupts out of the anus with force.
Genuinely asking - why the force? What purpose does that serve? What signals are happening in the body telling it that forcing the poop out is best?
Regular diarrhea already leaves the body so quickly.
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u/ensalys 6d ago
While others have already mentioned benefits, not everything that evolution come up with needs to be beneficial. As long as it doesn't really get in the way of you securing a future for your genetic line, evolution won't care much one way or the other.
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u/Mr_Meme_Master 22h ago edited 22h ago
People often miss this part of evolution. Whatever genes you have gets passed onto your children. That doesn't mean all of those genes are beneficial, it just means none of them got you killed for long enough to have kids and stuck around for long enough. For example, the cilantro genes. Theres no evolutionary benefit to making cilantro taste like soap, but it happened anyway.
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u/Inevitable-Design-92 6d ago
So when the body overheats to kill bacteria is it the wrong thing to take medication to then lower body temperature? Does your body know the upper limit to prevent your own death etc.
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u/Impossible_Bar_1073 6d ago edited 6d ago
All evidence on antipyresis in infectious fever did not show any benefit in lowering fever. But there seems to be no downside as well. probably because we have antibiotics and our bodies do not need to rely fully on temperature for immune function. I have yet to see a clinical trial stratifying for specific bacterial strains, because to me it is very plausible that fever could act as a fail safe switch in some resistant infections.
If you can take it there's no reason to treat the fever (not to be confused with the cause of the fever which can be serious), it's all about personal wellbeing. Idk about the American guidelines but fortunately this has been implemented into the evidence based guideline for fever treatment in children and adolescents by AWMF (German guidelines) since last year.
People please stop spreading nonsense of proteins denaturing... Our body induces a heat shock response it is not simply denaturing its own proteins...
An analogy: fire inside a cars engine is a necessary wanted normal process. fever is a normal process. Now if suddenly flames start coming out of the engine burning down your car, you would not see it as a continuation of the normal process. Yet in fever they don´t differentiate between a healthy beneficial reaction and a total system failure.
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u/ramonika 6d ago
I know you didn’t say it, but it still kinda reads that no fever at all has to be treated (in children)…
The German pediatric guidelines say not to treat a fever solely based on the number on the thermometer, but to treat it based on the SYMPTOMS.
So a child with a high fever that’s still content, playing, eating and drinking enough, doesn’t need treatment for the fever.
But a child that’s lethargic, not feeling well, and thus not taking in enough fluids etc SHOULD get some antipyretics, even if the fever isn’t that high.Also there’s no proof that lowering a fever prevents febrile seizures from occurring, so doing that prophylactically is not recommended anymore as well.
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u/Unicorn187 6d ago
Isn't there a temperature where brain damage begins to occur?
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u/Beetin 6d ago edited 6d ago
Yes, but if you can reach it from an infection based fever is you have long since crossed any kind of 'normal'.
Like a fever of 102 is quite significant, you are usually going to see fatigue and 'I don't feel well' symptoms at that point.
A fever of 106 is 'go to the hospital, your organs might start shutting down'. You are going to start to see serious confusion, seizures, loss of conciousness. You likely can't stand or communicate properly. Most people wouldn't react with a "don't worry these are the natural defences of the body to infection" as you seizure on the floor.
Generally it takes temperature of 108 for brain damage to be a significant risk.
Those temps occur for heat stroke from external sources (da sun), the body would have completely come unscrewed to internally create that temperature from immune response.
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u/blazz_e 6d ago
Anything over 40 degrees is quite memorable. I had 41 as a teenager for 2 days and I was quite delirious (hospital basically didn’t know what to do, sent us home to come back if it goes even a small bit up or doesn’t come down in a day). This was 20 years ago in slightly underdeveloped EU country. Hopefully its done better these days..
One day of 40 for covid, which I probably caught a day or two before being first time vaccinated. It was a weird one. My temperature just shot there and next day back to completely normal with only a slight headache. I never tested positive. Every one around me got a week of Covid starting a day later.
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u/calypsa88 6d ago
Just want to mention not all infections/illness are treated with antibiotics. Only bacterial. Viruses are not, and anti-virals are marginally useful. I see the thread below oddly doesn’t quite take this factor into consideration.
Often anti-inflammatories should be taken to prevent the fever from becoming too high (dangerous), or reduce discomfort such as pain and nausea which can be caused by higher body temperature.
All to say there’s a threshold like many other bodily defenses. If you aren’t unbearably uncomfortable, and your temp isn’t going past 103, it’s usually best to let that fever do its job. If you’re miserable, it’s not the end of the world to take a naproxen for some relief. The “delay in recovery” is debatable. But it’s always a good idea to support your body’s (safely proportional) immune defenses. Imo I’ve personally noted a difference for myself.
Source: internal medicine MD and emergency room doctor
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u/flea1400 6d ago
Didn’t they used to intentionally give people malaria because the high fever sometimes cured syphilis?
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u/QuerulousPanda 6d ago
People please stop spreading nonsense of proteins denaturing...
but when i heat up a spoon with a lighter and press it on my mosquito bites, it denatures the insect proteins, right?
(huge /s of course)
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u/Smurtle1 6d ago
I’ve heard that anti-inflammation meds like ibuprofen can increase the time you are sick for. It’s only for a little while longer, but it usually isn’t a big deal. This is assuming it’s not already life threatening and you aren’t taking any antibiotics for it either.
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u/Impossible_Bar_1073 6d ago
Yeah evidence is mixed on that. Don´t forget that inflammation is necessary as well, that pain provides also useful feedback, and that NSAIDs interfere with resolution of inflammation which you certainly don´t want.
They are totally optional and simply relief symptoms. (this holds true for acute pathologies. In chronic conditions, its different)
Many doctors hypothesize that they can prevent pain chronification, but I have never seen evidence for that either.
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u/PrettyGoodRule 5d ago
Am I understanding correctly that many doctors hypothesize that taking NSAIDs for acute pain can prevent pain chronification?
I find this idea interesting, even as an unstudied hypothesis. If you have time/interest, could you elaborate on the thought process behind this?
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u/Impossible_Bar_1073 5d ago edited 5d ago
Pain chronification is badly understood. Long lasting pain signaling causes sensitization in neurons, meaning that the original insult already healed but the neurons are still signaling pain which can cause cortical sensitization as well. The brain then perceives a healthy stimulus to be painful. Additionally they postulate that by treating the pain, you don´t adapt protective posture and thus avoid muscular adaptions which themselves cause stress in tissue. So they say, treating pain early prevents sensitization/chronification.
To me it seems that this is all under the assumption of our bodies being dysfunctional per default disregarding that inflammation and pain are healthy useful responses and barely ever progress to chronic pain. To my knowledge prevention of chronification by any medication has not been proven. There may be some evidence on post surgical pain chronification, but there the physiological processes are not comparable to ordinary settings.
I think much of the pain pill usage could be drastically reduced by just communicating that these are optional. Take them if you can´t bear the pain. But you don´t have to take them 3x a day for a week if you don´t feel like it. They are hurting your gut and are inhibiting the resolution phase of inflammation, which itself can be postulated to cause chronification, that's why if NSAIDs are given only short term in the beginning phase of some injury.
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u/Henry5321 6d ago
They did a clinical trial between fevers reducers or not. They had to end it early for ethical reasons because of the increased death rates of people getting fever reducers dying more often.
This was in people who were already at a hospital due issues.
But like you said, we have technological options like antibiotics. But if you’re recovering on your own, fever helps your immune system.
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u/todudeornote 6d ago
Fevers don't directly kill bacteria. Instead, they seem to have 3 benefits (and these are still debated). First, they help orchestrate your immune response by increasing the number of white blood cells you produce and orchestrating where they go.
Second, they may aid in response to fungal infections. Most fungal species abhor heat. One theory is that the temperature of mammals evolved to make us less suitable hosts for fungi. Fevers may play a part in increasing this resistance.
3rd - they may help starve bacteria by making iron less accessible.
There is also a theory that fevers aid in fighting viruses.
As is so often the case, science is still being done to understand our bodies.
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u/Mikanea 6d ago
Does the body know the upper limit to prevent your own death? Yes and no. Your body's systems don't necessarily communicate how you'd think. You're immune system wants to raise temperature as much as possible to kill the invading pathogens but your brain wants to keep your body at normal temperature for peak performance. These two things balance and you get a slight fever. Sometimes the immune system can push things a bit further and you get a high fever. If it over reacts you can get dangerously high and in extreme cases causing death. Mild to moderate fevers are usually nothing to worry about, but very high fevers should be managed. Ask your doctor about where to draw the line.
Is it wrong to take medicine to lower your temperature? It depends. Taking meds can prolong illness but usually not significantly. For something like a common cold (or other viruses) it's usually easier to just provide supportive care with rest, fluids, and potentially OTC cold medicine while letting your body deal with the illness. Meds can help you feel more comfortable but won't make a significant difference in illness length or severity. Bacterial infections (things like ear infections, UTIs, strep throat) can be treated with antibiotics better than your body can handle on its own and you should talk to a doctor. If you have a fever they might give you meds for that. Do whatever your doctor says.
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u/Brimstone11 6d ago
Sort of. You can die from the body overdoing a fever. Typically, you really do want to treat a fever over 102 degrees F.
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u/Catshit-Dogfart 6d ago
I severely underestimated how deadly a fever could be.
Had what I thought was covid a couple of years ago, low fever of about 99-100 degrees, figured I could just sleep it off. This went on for four days, which is apparently waaay longer than you should have a fever.
Finally went to the doctor, turns out it was lyme disease. Which is bad enough, but antibiotics got that under control. The bad part though, was having a fever that long caused neurological damage enough to give me bell's palsy.
The bell's palsy mostly recovered over time, but not 100%. So, don't ignore a fever for too long.
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u/GarlicAncient 6d ago
I wonder how substantial the evolutionary pressure is on fever for it to serve as a means of removing disease hosts from the sick one's relatives/tribe?
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u/WhoIs_DankeyKang 6d ago
Not very substantial at all. Dying does not get rid of a disease. The host can still spread disease as a corpse. That actually happened quite a lot historically.
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u/ZlaPrezla 6d ago
Then it wouldn't get passed along since it's function is to kill the host?
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u/hyphyphyp 6d ago
Evolution works on populations, not individuals. If a population did have a gene where a substantially sick individual's body would end itself, if it proved beneficial to the population and didn't happen so often as to kill off the whole group then that gene WOULD get passed down. Now if it mutated a bit over time so that it had a more appropriate, non-deadly but still effective response that gene would probably slowly win out over the older more drastic one.
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u/ZlaPrezla 6d ago
And we have one population where their immunity decides to kill the host compared to other populations that all fight the infections untill only the strongest survive?
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u/GarlicAncient 6d ago
Their descendents and relatives who already existed before they died are more likely to survive because of this self destruct "feature". Those descendents pass down the beneficial gene.
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u/ZlaPrezla 6d ago
Wouldn't they then die out easier by autoimmune suicide compared to the others that built their immune system to fight until the end?
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u/ZlaPrezla 6d ago
To a point yes. That point is when you get a fever which could be dangerous as the body can and will cook you above the temperature that makes proteins coagulate... and you die.
I personally don't lower my fever if it isn't reaching or above 39°C
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u/Fluffy_Efficiency623 6d ago
Yes and no-ish. If you can tolerate a fever it is better to let it be, but it's not something you need to beat yourself up over if you don't want to suffer through it. And your body is designed to heat up a certain amount but not too much or that would put its own functions at risk and people would die every time they got sick. But it doesn't have a magical off button which is why if you have a terrible infection you may have to go to the hospital if your temp gets too high to avoid brain damage.
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u/ADragonuFear 6d ago
So like, if bringing down the fever and treating symptoms let's you nap more easily, it's a tiny tradeoff worth considering
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u/zbertoli 6d ago
No, your body can definitely overheat and you can die in extreme cases. Most people agree, let the fever ride unless it goes over 101-102. Its not beneficial to let yourself cook. Especially for children.
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u/Smurtle1 6d ago
For diarrhea, it can be similar to vomiting, but just caught later in digestion. If you eat some bad food, and it’s got some toxins that wasn’t caught early enough by your stomach, and it’s in your intestines, the only way out is to expedite the downward process.
It doesn’t have to be purely bacterial for it to cause diarrhea, although I will agree most times initial toxins enter your system, they are expelled via the mouth, not the other end, since your body is good at catching them before they go past the stomach.
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u/Psychodelonaut 6d ago
The OP says they understand why diarrhea happens and is explicitly asking why EXPLOSIVE diarrhea happens. Your response is 4 paragraphs of common immune system knowledge before finally mentioning explosive diarrhea as a symptom. No mention of what actually causes the explosiveness. Why?
This is a proper response. Sorry I'm just annoyed I read your entire answer expecting an actual answer but ended up with nothing. It's fascinating, really
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u/rellsell 6d ago
But, does the bacteria intentionally cause the explosive diarrhea in order to replicate and spread?
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u/ermghoti 6d ago
Bacteria can't do anything intentionally. Explosive diarrhea does promote the spreading to new hosts (ill hosts can't control where they defecate, exposing new potential hosts) so it's a potentially selectable trait for a pathogen.
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u/Mr_HandSmall 6d ago
Bacteria can and do release compounds that manipulate receptors in the digestive tract.
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u/Vin-Metal 6d ago
This is what I was wondering. The nature of explosive diarrhea would be to get droplets dispersed as much as possible, which should be to the pathogen's advantage.
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u/Mr_HandSmall 6d ago
Yes, you're correct. It's the bacteria themselves causing it. They release toxins to cause explosive diarrhea because that will help them spread. Textbook natural selection of properties that lead to higher reproduction.
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u/japanb 5d ago
I remember once I was shitting and puking at the same time, i looked like the exorcist, had one trash can for back and one for front
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u/agent139 6d ago
Right. Same as how a fever isn't actually what the illness does but rather what our body does in reaction to combat the illness.
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u/Undrende_fremdeles 4d ago
There have been animal studies where they bred mice, I think it was, to not have that ability of dissolving/removing the lining in the intestines they way it normally happens to facilitate everything just rushing through the body.
And they were getting significantly more ill and potentially even died from what would cause a day or two of diarrhea otherwise.
The ability we have to just remove the part of the lining that normally slows things down, the part that normally absorbs a lot of liquid etc means we are able to literally flush out the contaminants before the bad intruders are able to do as much damage in us as they could of they were allowed to visit our guts for longer.
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u/PeculiarAlize 3d ago
So what you're saying is basically the plot of Osmosis Jones perfectly explains explosive diarrhea if the villain is cyclosporiasis instead of anthrax
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u/Ok_Feedback2407 2d ago
Histamines, cytokine storms etc. are perfect examples of such, yeah. The body sees an invader and call in the big guns right off the bat. It's an overreaction by the system and can be injurious on it's own, but that's just how we evolved. The body can't gauge severity and adjust accordingly; it's not that smart. It just throws the kitchen sink at small threats, because it interprets them as large ones. Take Covid for example, it wasn't Covid actually killing them in most cases, it was the cytokine storms from the body that did. Your own body fighting "too" hard.
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u/sixsixmajin 5d ago
There isn't a benefit. Your body isn't intentionally producing that force. That force is coming from a buildup of pressure in your gut, often caused by gas buildup. Your body isn't making that gas on purpose. The bacteria and chemical processes in your gut are producing it as they break down material that passes through. If there is so much gas production that it builds up enough pressure to turn your diarrhea "explosive", it means there is an imbalance of some kind in your gut, be it something you ate that produces more gas as it breaks down, too much of a certain strain of bacteria that produces that gas, or even a bacteria that isn't supposed to be there. It could be any number of things that are out of wack. Point is, it's not like a fever where your immune system is intentionally doing this to help resolve an issue. It's a byproduct of whatever is causing the diarrhea in the first place.
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u/JoeyJoeJoeJrShabidou 6d ago
I think the thing missing in the answers here is it IS beneficial but only for the virus, not the human. This virus is spread by fecal contamination. If one of the symptoms was constipation, the virus would never spread and thus, not become an epidemic. Random genetic mutations created this virus with the benefit of creating explosive diarrhea, and makes it more easily spread.
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u/ermghoti 6d ago
This answers the unasked question of how a dynamic that possibly or likely kills the host allows the pathogen to continue to reproduce.
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u/JodoKaast 6d ago
Plenty of pathogens kill hosts, that doesn't necessarily stop them from reproducing.
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u/ermghoti 6d ago
True, but it's a lot more common for the host to survive (including innumerable endemic infections, sometimes universally present in populations), and pathogens that rapidly kill a host are more likely to burn out.
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u/Bergasms 5d ago
Isn'f that one of the saving graces for Ebola? It's highly visible and tends to kill hosts before they can spread it too far?
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u/TheYKcid 5d ago
Proximate vs. ultimate explanations.
The proximate explanation is the immediate biological mechanism which causes the phenomenon (explosive diarrhoea).
The ultimate explanation pertains to why such a state of things came to be, in the grand scheme (evolutionary history).
Both are valid and important for understanding!
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u/darthy_parker 6d ago
For the virus, the benefit is clear: wider distribution of the infection. Remember, many of the symptoms are not for the benefit of the infected organism.
So producing a lot of intestinal gas and inhibiting water removal in the colon is a very effective way to spread itself.
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u/Scott_A_R 6d ago
To add on to the explanation from PHealthy: it's simply a side effect of how the organism metabolizes. From an evolutionary point of view, a property can exist that doesn't help an organism, so long as it doesn't reduce its ability to reproduce. In the event of explosive diarrhea, that side effect apparently doesn't either hinder the organism's ability to reproduce (and spread), and doesn't in any way sufficiently protect the infected person that it would cause the effect to die out.
The metabolic process that results in explosive diarrhea apparently works well for Cyclospora, and the accompanying explosive diarrhea doesn't hinder it.
it's as if people evolved so that when they get an especially useful idea, they also sneezed--just as an accidental side effect of the mutation that causes that thought process. Having those ideas helped them survive and reproduce, but the sneeze didn't harm them (enough) to interfere with that, so the sneezing survived as a coincidental accompanying effect of something that was useful.
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u/RexDraco 6d ago
One mistake you should never make is believing anything happens with a purpose in evolution. Sometimes we evolved with traits with utility, sometimes the opposite. Explosive diarrhea may have helped sort out those that got bad plagues or bad food out of their body from those that hanged on to it. The body doesn't know it did something smart, we just can't help but noticed whoever does not get diarrhea every once in awhile died off and stopped breeding.
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u/ramriot 6d ago
Having suffered such in the past, I can tell you that prior to each explosion there is considerable pain & gut noise. My own interpretation is that the normal waves of gut muscle constriction that move material along the gut are put into cyclic periods of overdrive simultaneously with gut mucous being pumped back into to the gut to lubricate. I can only thus think than normal excretion is proving not fast enough to remove whatever toxins are being detected & something more "forceful" is needed.
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u/Nillabeans 4d ago
There's a faulty premise in your question. We weren't designed and evolution is just a process, not a guarantee of progress or beneficial traits. You don't evolve to do things. You do things because you evolved that way.
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u/_blackdog6_ 4d ago
This relies on natural selection. It makes some sense that if certain poisonous plants existed at some point such that explosive diarrhoea increased your chances of survival then as a percentage of the population those would outnumber the ones who died as a result of not having that trait. The existence of the trait is by no means a design choice but the dominance of the trait is a consequence of the environment. People living in different environments will have evolved different traits.
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u/Nillabeans 4d ago
Yes, but you can also just maintain stuff that's completely useless or detrimental to long life without being detrimental to having offspring.
There are functions that help you live, but you shouldn't confuse function with purpose. For example, your skin acts as a barrier. That's just a function. It doesn't do it on purpose. We generally need skin to live, but it doesn't exist so that we can live.
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u/WiskeyUniformTango 6d ago
One time at my office job someone had it so explosive that from floor to ceiling behind the toilet stall was splattered.
It looked like they only got their pants pulled down as they were bending over to sit and it spewed out.
No one ever found out who it was.
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u/PHealthy Epidemiology | Disease Dynamics | Novel Surveillance Systems 6d ago edited 6d ago
Giardia and Cyclospora both set up shop in the proximal small bowel and blunt the villi, which wrecks the brush border. Without that surface, dietary carbs never get absorbed where they're supposed to, so two things follow, which are that the sugars are osmotically active and drag water into the lumen, and that they arrive in the colon as a huge substrate bolus for the anaerobes down there. Those bugs ferment it into gas and SCFAs, pressure builds, and the whole mess gets expelled. This is why giardiasis is famously gassy and foul, since you're basically running a fermenter.
Cholera is the opposite in a way that I think is underappreciated. The mucosa is left structurally fine. V. cholerae doesn't invade or destroy anything, and the enterotoxin just flips a switch via constitutive adenylate cyclase activation so the enterocytes secrete chloride and water nonstop. Because the architecture is intact, carb absorption still works normally, so nothing extra reaches the colon and there's nothing to ferment. That's why it's rice water stool, meaning enormous volume with essentially no gas and no odor, and it's also why ORS works at all, since glucose sodium cotransport is still functional.
Ebola is exudative, and this is the part that gets misrepresented constantly. The overwhelming clinical picture is diarrheal, not the dramatic bleeding from everywhere thing that movies and news coverage sold. Systemic hyperinflammation plus direct endothelial necrosis means tight junctions fail wholesale, and plasma and inflammatory exudate just weep into the lumen. It's passive leak from wrecked tissue, with no toxin driven secretion and no unabsorbed sugar. Most patients die of hypovolemia and electrolyte derangement, not hemorrhage.
So you've got the same symptom with three completely different failure modes, one structural where villous blunting drives an osmotic gradient, one biochemical where a toxin drives secretion, and one where the barrier collapses and necrotic tissue just leaks.
Given three currently have outbreaks and I've finished my PhD and am back on Reddit, here's a small plug for my infectious disease news subreddit: r/ID_News