Why do you feel itchy after running?

Answer 1

You're not fit! It will go away once you increase your fitness level. It's because your arteries are having a hard time with the oxygen levels in your body. It sends a signa to the brain for "itch"

Answer 2

I read somewhere that it is because your muscles are actually stretching and this causes an itching sensation.

Answer 3

sweat. And hair wrapped around with other hair.