Do hair and nails continue to grow after death?
Dear Straight Dope:
Whether it's true or not, the continued growth of hair, fingernails, and toenails pops up continually in fiction. But is it true? And how much growth can there be after the old beet juice stops circulating? Should we include with our organ-donor cards haircut and manicure instructions to the mortician?
It's not exactly true, but it's understandable how the idea came about. Unfortunately, books and Hollywood have done more to bloat this idea than any corpse ever could. So here's The Straight Dope.
Hair and fingernails aren't actually growing. Dead is dead. The only things growing after you're dead are worms, bacteria, and flowers. What is happening, however, is that the skin around the hair and fingernails will desiccate (i.e., lose water) and thereby shrink. When the skin shrinks, it retracts, making hair and fingernails look longer, as if they'd grown.
Think of it this way: a fifty foot tree grows in ten feet of swamp water. The visible part of the tree is 40' tall. A few months later, a drought causes the water level to drop five feet. Now the visible part of the tree is 45' tall. Did the tree grow in a drought? No, but you can see why people would think it did.
Hope that helps, and remember, don't try this at home!