The moment your hair cells leave the pores on the skin of your head, they die. Thud all hair is dead.
The moment your hair cells leave the pores on the skin of your head
Even before that. You pull a hair out, and if that specific hair follicle was still growing you should see a teeny-tiny bulb at the very end. That bulb can be up to a mm beneath the skin. The widest part of that bulb is where the hair cells begin dying and drying out. By the time it shrinks down to the width of the rest of the hair (and long before it emerges from the pore), all the cells in that section are dead. Only the base of the bulb has living, growing hair cells.
Are you implying that your fingernails were never cells of your body? How does that work?