Hair and nails do not keep growing after death. The skin dehydrates and retracts, making them appear longer. Growth requires living cells and stops when the heart stops.
A common spooky story says that hair and nails keep growing after someone dies. They do not. It is actually a clever trick played by the body. Here is why the myth persists and what is really happening.
After death, the body stops receiving water and begins to dehydrate. This causes the skin to dry out and shrink. As the skin on the scalp and around the nail beds pulls back, it exposes more of the hair and nails that were already there. This makes them look longer than they were before, but it is just an illusion. No new length is being added.
For hair and nails to grow, the body needs to create new cells. This process is like a factory that requires two main things: glucose (sugar) and oxygen. These are delivered by the blood. When the heart stops beating, the blood stops flowing, and the "factory" loses its power supply. Without oxygen and energy, cell division stops immediately, and so does all growth.
Doctors and funeral directors see this process firsthand. To prevent the skin from shrinking and creating this "growth" look, funeral directors often apply moisturizer to the hands and face of the deceased. This keeps the skin hydrated and proves that the change is about the skin moving back, not the nails moving forward.
Hair and nails need a living body and energy to grow. Once the heart stops, growth stops too. What looks like growth is simply the skin drying and pulling away, revealing what was already hidden underneath.