Answer:
What can go through glass without breaking it?
They try to beat me, they try in vain. And when I win, I end the pain.
I'm not man's best friend, I'm their enemy, I can mark your end, yet you do not see me, I am very small, but very tough, If you have me, then you have it rough.
How far will a blind dog walk into a forest?
What instrument can make any sound and be heart, but not touched or seen?
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?