The answer to this question is really quite simple. As many of you may know, the human body is essentially a big sack of water which is contained within our cells. When we die our bodies are no longer able to hold that water in, so we start to dehydrate. When our skin dehydrates, it gets pulled tight. And when it gets pulled tight around the hands, it may look as if the fingernails are growing, however it just the dry skin receding.
Similarly, hair does no grow after death – see Artem’s in depth answer here, with a bit more of the science.
Answer by Kyle Pastor
Question received via Facebook