Have you ever studied the face of a man shortly before and a few days after his death? Chances are that you noticed that his face was covered in stubble that was not visible before he died.
The same goes for the nails: they seemed longer after somebody’s death than before. We can therefore deduce: your hair and nails keep growing after you die. However, it could be the exact opposite.
So how does it work?
Your eyes are not deceiving you; the stubble on the face of the deceased is really there. It is real but that’s not because the hair on the lip, jaw and cheeks have grown. All processes in your body stop after you have taken your last breath.
The necessary oxygen supply which is needed for the growth of hair and nails stops. Your lungs stop working and your blood circulation comes to a halt. So it is impossible that you produce new cells in your body. Also, your hair and nails are dead in any case even when you are alive. They consist of lifeless matter.
The appearance that your hair and nails continue to grow is because the muscles in the skin contract a little when a body stiffens up. Also the skin of a deceased person dries out. In other words: it is not the hair and the nails that grow, but the skin that ‘shrinks’. You could compare it to a 20m high tree of which the bottom 2m is under water.
The tree would not be taller if the water level drops after a period of extreme drought. You can see more of the tree, but physically nothing has changed the stem.