I recall this question coming up on Reddit with some regularity (no pun intended). The typical answer I saw was something like "your rectum has a really strong immune system"

That part of the body, like your mouth, has features that greatly reduce the chance of infection because they are the entry and exit points for foreign objects or waste. It is complicated how it all works, but in short your body really needs those parts to bot get infected, so it adapted ways to keep that from happening.

That was the explanation I got from the doc when mine first showed up.

Edit: All hail the rise of the butt bots!

I am not qualified to answer this, but I did once see a similar question asked on Reddit. The best response I saw was from a commenter whose name I can't remember, else I would credit them.

That commenter said that his infant daughter had required an operation on her rectum. The commenter asked the surgeon how the surgery site could possibly not become infected and was told "the asshole knows how to handle shit."

That answer seemed reasonable to me and I probably will never forget it.

Probably a lot of us do have infected buttholes, but just don't realize it. It's a silent but deadly epidemic.

Even the bacteria doesn't want to eat your ass.

A bidet helps. Gentle splash of water vs scratchy paper.

Username checks out, it was the first word out of my mouth when I read this question.

Good question though, looking forward to (hopefully) informed answers.

Fairly sure it's because of the difference in environment. Gut bacteria tend to be anaerobic fermenting species, whereas the external part and blood are more aerobic. It's been a while since i did physiology and microbio tho, someone correct me if I'm wrong.

This is a genuine question I've wondered about a lot. Kudos for oddly realistic originality.

Basically blood pressure keeps most things out, and you probably wouldn't purposely rub a meaty turd in an open wound regardless. I hope.

https://en.wikipedia.org/wiki/Abscess

maybe less common due to adaptive immunity to familiar bacteria

could still happen. and stds are an obvious example.

I'm in my 40s and never had hemeroids. Are they really that common? Or maybe I have and I didn't know (but surely I would, right??)?

kind of unrelated, but hemorrhoids are only common because something like 95% of people don't eat the (already low) recommended amount of fiber. eat lots of fiber, people.