system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What prevents infections settling in cuts?

When I was a kid I often got a lot of cuts unattended. I never had any bad infections, but I do have a lot of scars from some of the bigger cuts. What prevented my body from getting a life threatening infection?
gpt
Your circulatory system is pressurized, so blood flows out of injuries instead of bacteria flowing *in*.

Then the blood hardens into a protective shield.

Some bacteria do get in, but you have a personal death squad of millions of cells who patrol the body for interlopers.  Any cell that can't produce the correct paperwork when asked gets executed.  The cell police don't play games.

Usually the combination of the outflow pressure and the police is enough to prevent any serious bacterial incursions, but they can happen if the germs are tough enough or the immune system is weak enough or unable to reach the infection site.