Scales have been collected from different protected areas of the body for periods of three to six weeks. Crude soft horn production was five to ten times higher on the scalp, forehead, and palms than elsewhere. The synthesis of keratin diminishes centrifugally from the scalp downwards and outwards (excepting the palms and soles).
The total production of crude soft horn per day for the entire skin surface is 0.5 to 1.0 gm. The nitrogen loss via skin shedding is thus trivial.
HERBERT GOLDSCHMIDT, ALBERT M. KLIGMAN. Quantitative Estimation of Keratin Production by the Epidermis. Arch Dermatol. 1963;88(6):709–712. doi:10.1001/archderm.1963.01590240033007