Eli5 How do people still have freckles or tattoos if the skin cells are new every three months?

Question

Eli5 How do people still have freckles or tattoos if the skin cells are new every three months?

In: 12

Answer 1

The skin cells that are replaced are mostly the top layer. The bottom layer that produces the cells that get pushed to the top are stem cells. They are effectively immortal and reproduce by coping themselves. These are the cells that are ultimately responsible for freckles, along with the cells that produce melanin. Tattoos go into this layer. So, while tattoos can fade over time, the ink is deep enough to not entirely disappear.