ELI5: Food Poisoning

Kent - April 9, 2023

ELI5: How exactly does food poisoning work? How does the body know that the food is contaminated and which way to expel it out? How does it know when things are safe again?

The food gets digested and nutrients get taken in by the body. If it’s contaminated, let’s say by salmonella, the bacteria also makes it into your body.

Your immune system will quickly find the bacteria, and try to kill it. Part of that means purging the digestive tract (diarrhea and vomit) to get rid of the source. Fever is added to kill off the bacteria that already made it past your digestive system.

It knows it’s save when there are no longer any offending bacteria in your body.

Of course it’s more complicated than this, but hopefully you understand the basics now.


To those of you bitching about me not explaining microbial toxins and things like that, shut up. It’s explain like I’m 5, details like that don’t belong here. (Not to the people just politely added on info, that’s always welcomed)

E.coli and other bacteria are super tiny things that live and grow in food. As they grow and make more bacteria, they produce toxins (toxins are substances that make you sick), some of the toxins get destroyed by cooking, but some are still there even when cooked. When these toxins hit your insides they make your belly upset. Your body doesn’t want you to eat any more toxins, so you can even feel sick just looking at or smelling food.

Looking at some of the other answers I’d like to clarify. Bacterial infections in the bloodstream are known as sepsis.

When you get e.coli infection, it is actually infecting your gut lining. There are different types of infections, some break the cells of the gut lining and can cause bleeding, other times it changes they way the cells exchange water resulting in really watery poops.

As other people have said, it is a built-in mechanism of your body.

Bad stuff detected > Get it all out!

The problem is that once “trained” it is hard to overcome the reaction.

I got food poisoning from my High School Cafeteria. I ate a bad cheese burger that had ketchup and pickles on it. I spent 3 days in the hospital; running at both ends and plugged into a plethora of IV’s.

I cannot eat a cheeseburger with ketchup and pickles to this day. I get to “enjoy” a stomach purge just as I have the taste epiphany of cheese/ketchup/pickles.

It can be quite distracting for other restaurant patrons if my burger is prepared with those three magic ingredients.


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