system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If we can use the rectum for effectively absorbing suppositories, how come we don't get blood poisoning from all the bacteria and waste minerals in our faeces?

It doesn't make sense to me.
gpt
Our digestive tract has a pretty strong barrier (lots of IgA antibodies that act like a web to trap) that prevents bacteria from crossing into the blood. Bacteria (or viruses) have to pass either between or through epithelial cells in order to enter the blood. There are numerous immune cells present to prevent this from happening. Drugs that are absorbed in the intestines are generally lipophilic (fat-loving) and can cross the fatty cell membranes of epithelial cells (think about "like dissolves like") and get into blood.

This is a gross oversimplification, if you want more detail just message me!