Answer:
I am made by nature soft as silk; A puffy cloud white as milk; Snow tops this tropical crop; The dirtiest part of a mop.
Take off my skin I won't cry but you will.
You use me between your head and your toes the more I work the thinner I grow.
In my life I must bare my bloodline I must share.
I am what one cannot keep, two cannot hold, and three cannot destroy. What am I?
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.