Answer:
I am a box that holds keys without locks, yet they can unlock your soul.
Take one out and scratch my head I am now black but once was red.
What do you throw out to use and take in when you're done?
I'm tall in the morning and short in the noon. I disappear at night but I will be back soon.
When they are caught, they are thrown away. When they escape, you itch all day.
You use it between your head and your toes, the more it works the thinner it grows.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?