The bulk of dust in your house is dead skin from the people who live in it. The skin is continually renewing itself from below and part of this process is the shedding of dead cells. This creates a lot of dusting. As always seems to be the case with the skin, it is fascinating to look into the details of the process. The bottom layer of the skin is the junction of the dermis with the epidermis. Cells from the dermis migrate upwards, losing their fluids and becoming more squashed as they get nearer to the surface.