Answer:
Searing 'cross the pitchΒ-black skies, I scream in celebration, Yet moments later, my outburst through, I am naught but imagination.
All about, but cannot be seen, Can be captured, cannot be held, No throat, but can be heard. Who am I?
I always follow my brother but you cannot see me, only him. You cannot hear him but you can hear me. What are we?
I cost no money to use, or conscious effort to take part of. And as far as you can see, there is nothing to me. But without me, you are dead.
Come up and let us go. Go down and here we stay
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?