Answer:
Tear one off and scratch my head, what once was red is black instead!
Itβs so fragile even just saying its name can break it. What is it?
Watches students at the prom to make sure there's no funny business.
What is so delicate that even mentioning it breaks it?
I start in little but I end in full, you'll find me in half and complete.
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?