This does not happen. It is simply not true that hair and nails grow after death.
After a person ceases to be among the living, their life, and energy supply (i.e. the blood) no longer flows throughout the body. That’s because the heart has stopped pumping it and because the blood transforms from a runny liquid into non-functional paste-like sludge that stays in one place.
Therefore, because the cells that produce your hair and nails do not receive a fresh supply of nutrients, including oxygen, they can no longer power the important cellular processes responsible for life and growth. Consequently, cells in the body begin to die within seconds of a person’s death.
The reason hair and nails “grow” after death is because of an illusion. Hair and nails are very hardy, non-living, structures. As the living tissues and cells around the hair and nails begin to dehydrate and break down, the skin shrinks back, making it seem like the hair and nails have become longer in relative proportion.
Just think of it this way: in the winter, go outside and place a stick vertically in some snow. The stick can be the hair or nail. The snow around it is like the living tissue around the hair and nail. As the snow around the stick “dies” or melts away, the stick will “grow” longer and longer despite actually staying the same exact size.
Answer by Artem Cheprasov
Question from Eugene Pirko
Image source: winterofdiscontent, on Flickr