When I first read about this topic I did not believe it at all…. I was thinking, why do humans even shed skin? I know that sometimes we have some dead skin, and they fall off, but those are so little amounts of skid lost. 40lbs is approximately 18.1kg. Actually, humans shed their skin every 25-45 days and we get a completely new layer of skin. Starting in our stratum basale(one of the layer of the skin), new cells replace old cells (through continuous mitosis) and push old skin cells, which are being keratinized, up to the free surface of our skin. When the old skin cells reach the top, they are dead, and they flake off without us even noticing half the time, (unless our skin is really dry then we notice) As a result, every 25 days we can have a brand new epidermis!