Why is it when we get a cut in our mouth(the dirtiest place ever) does it not get immediately infected? ELI5
In: Biology
Because you have an immune system that is constantly fighting infection, 24/7, 365
Every single cut, tear, scratch, scrap, peel, you ever get almost instantly has outside bacteria getting into it. And then slam or instantly your immune system is fighting those bacteria and keeping them from getting a foothold. And 99% of the time it succeeds and expels the invades.
But every once in a while, they fail, the bacteria get an foothold, and you get an infection.
Just as it is close for bacteria to enter the bloodstream from a mucous membrane (like the mouth), it is close for white blood cells to leave the bloodstream and attack bacteria that are attempting to do harm.
The mouth also has a high concentration of immunoglobulins, mainly immunoglobulin A, which neutralizes a lot of bacteria in case they try to proliferate too much.
Infections come from bacteria (and viruses), but not all bacteria is bad! Your mouth contains lots of bacteria that helps protect itself from harmful bacteria – the kind that cause infections, for example. We see mouths as dirty because it’s how a lot of common viruses spread to other people. Your spit can give someone else a cold, but it can’t give you an infection.
Our bodies are very good at dealing with our own germs (microbiome), but if you bite somebody else, the bite has a high chance of getting infected. Since they aren’t used to dealing with our blend of germs, it can cause them infections quite easily
>our mouth(the dirtiest place ever)
The human mouth does harbor lots of bacteria – however, it seems far from the “dirtiest” place on our bodies. Much of the bacteria is beneficial, aids in digestion, and helps keep your teeth clean. Other bacteria can cause gum and tooth diseases, but isn’t actively trying to infect your cuts. Along with a very active immune system in the mouth, cuts here often heal faster than other places on the body.
On the other hand, a cut in you lower intestine (which I would consider much more “dirty”) can quickly become a real issue.
The other commenters are exactly correct, but here’s some more detail. The surface of your entire digestive tract, from mouth to butt, has a layer rich in immune system cells because these areas are so delicate and also filled with bacteria. This layer is called the lamina propria. [Wikipedia has a diagram](https://en.wikipedia.org/wiki/Lamina_propria).
The immune system is an amazing thing. Interestingly, this is the same reason some immunocompromised folks have to take antibiotics before they get dental work. The increased likelihood of physical trauma to mouth tissues means more opportunity for infection in that population specifically because they lack the proper immune response that protects you from such opportunistic infections.
Reddit is once again the coolest place! Thanks so much for the responses!
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