Tattoos are permanent because of how the ink interacts with your skin and immune system. When a tattoo needle punctures the skin, it deposits ink into the dermis, the layer beneath the epidermis. The dermis is more stable than the outer layer, which sheds regularly.

Your immune system plays a crucial role in this process. When the ink is deposited, immune cells called macrophages rush to the site to engulf the ink particles, treating them as foreign invaders. These macrophages hold onto the ink particles, keeping them in place. Even when these cells die, new macrophages take over, ensuring the ink remains in the dermis.

This continuous cycle of macrophages capturing and retaining the ink particles is what makes tattoos last a lifetime.