Answer:
What gets sharper the more you use it?
What goes up and down but does not move?
I run cold and hot, I look blue but am red. What am I?
What has roots that nobody sees and is taller than trees. Up up up it goes and yet never grows?
The person who makes it sells it. The person who buys it never uses it. The person who uses it never sees it. What is it?
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?