[tamsinbell (OP)]

Dan asks:

"I heard that our entire body (bones, skin, nerve cells etc) renews itself every 7 years. So why do tattoos or scars last a lifetime?"

Any idea? Post below...

[chris]

Slightly tangential to the question, but this is an interesting interview from a previous edition of the Naked Scientists Podcast on the history and techniques of tattooing.

[chris]

Meanwhile, here is the actual answer you are seeking; we did it as a Question of the Week:

"Why do tattoos last so long?"

[evan_au]

I heard that some tattoos use iron oxide as a dark pigment.
Sportsmen with large areas of black tattoos have suffered minor burns when given an MRI to investigate injuries.

Any truth in this rumour, @alancalverd?

[RD]

The body does attempt to get rid of tattoos ...

Translocation of tattoo particles from skin to lymph nodes. Upon injection of tattoo inks, particles can be either passively transported via blood and lymph fluids or phagocytized by immune cells and subsequently deposited in regional lymph nodes. After healing, particles are present in the dermis and in the sinusoids of the draining lymph nodes.

https://www.nature.com/articles/s41598-017-11721-z

[Bermendy88]

I am also interested to know about this. No idea how this could be permanent.