Blood
 

If you see a kid has a cut or scrape on his arm after a play, should you stop the clock ("my time") and get him off the field?

ALWAYS.

Why would you think not?

It has been a rule in high schol for a few
years now.
The worst situation I ever saw was when I worked
one of the first high school games at the then P and C
Stadium in Syracuse. The artificial playing surface was
very rough and the kids were all scuffed up and bleeding
from their elbows,etc. I had them all go off and get wrapped
and bandaged. What a mess. The word got out quickly and
teams playing there later on came with good padding and
protection.
I'm not sure if they even play football there any more.
It sure was not a surface for football.