top of page

LuxeSci Show Notes: S2E12b - Tattoos

I decided to do a little mini episode since I really wanted to talk about tattoos and Dimos questioned whether or not tattoos were luxury items.  While I’m not so sure they are luxury items, I do consider them art so is a little science behind tattoos.


  • Tattoos have been used as a form of body modification for thousands of years.

  • The oldest tattooed mummy is Otzi dating back to 3250 BCE

  • The oldest figurative tattoos were discovered on two mummies from Egypt which data between 3351 and 3017 BCE

  • Ancient tattooing was most widely practiced among the Austronesian people of Taiwan and South China and then to the Indo-Pacific

  • The word comes to English from the Samoan word Tatau meaning to strike, which is from the Proto-Oceanic word, sau that refers to the wingbone of a flying fox that was used as the instrument for the tattoo process

  • This is not be confused with the British word, tattoo, which is a military drumbeat or performance which is derived from the Dutch word, taptoe.


  • So how do tattoos work?  Contrary to what I thought, the ink is not injected into your skin.  Instead, the needles function more like the tip of the pen, with the ink flowing off the tip and into the hole that the needle makes.  Capillary action then draws the ink down into the dermis (skin)

  • Capillary action - movement of water within spaces of porous material due to the forces of adhesion, cohesion and surface tension - or - the process of liquid flowing in a narrow space without the assistance of, or even in opposition to, any external forces like gravity.

  • But why does a tattoo last? Does it stain your skin?  I read a great article in Popular Science about this that references research published in 2018 by Sandrine Henri and Bernand Malissen of the Centre dI’mmunologie de Marseille-Luminy in the Journal of Experimental Medicine helped to shed a light on how tattoos endure in the skin

  • They were research how the naturally occurring pigments interact with macrophages in black mice.

  • Macrophages - your immune system’s vacuum cells. Or more scientifically, macrophages are white blood cells that surround and kill micoorganisms, remove dead cells and stimulates the action of other immune cells.  They also like to “eat” foreign matter in the body. 

  • They are part of your innate immune system, which is the non-specific portion that is first activated by foreign invaders.

  • Dr. Henri and Dr. Malissen found that the mice macrophages would eat the dark pigment of the black mice when the cells that create the pigment died. They wondered if the macrophages did this with tattoo ink as well

  • Using mice where the macrophages can be depleted (killed off), they tattooed the mouse, depleted the macrophages and found that the tattoo persisted and eventually new macrophages arrived to re-ingest the ink. 

  • So is tattoo permanence actually due to lasting macrophage turn-over.  When one dies and releases the dye, it’s taken up by another macrophage?

  • This would have interesting implications in tattoo fading as well.  Perhaps its not all due to the sun bleaching but maybe also due to not all of the ink being re-ingested with each round of new macrophages so the tattoo fades

  • Note - human macrophages do not turn over as quickly as mice

  • A study published in the Journal Dermatology in 2023 by Marius Kroger et al showed that carbon black ink pigment was found in macrophages, mast cells and fibroblasts in the dermis and in keratinocytes, dendritic cells and basal cells in the epidermis (which is continuously renewed).  This was found even in tattoos that are 9 years old. This suggests that there may be several cell types involved in tattoo recycling so-to-speak.

  • Bonus info - tattooed skin showed collagen I structures with higher directionality with greater firmness and decreased elasticity - like scar tissue

  • So how does laser tattoo removal work?

  • Fundamentally - the laser breaks down the tattoo ink particles into smaller pieces so that the immune system can remove them from the body.

  • However, due to the re-ingestion we’ve talked about, this takes multiple treatments to accomplish

  • In order to accomplish breaking up the ink particles, the ink must be heated quickly before it can cool.  This means that the pulse durations of the laser need to be short with high heat.  This is usually done with nanosecond or picosecond lasers.

  • This has the advantage of not damaging the skin too much as we talked about with our episode on spray paint and how to get spray paint off of monuments.  That was a femtosecond laser - even shorter pulses

  • What if you don’t want to do laser removal - are there other options?

  • There are many other options, though they may not leave the skin looking as it did before the removal:

  • Surgical techniques - excision of the skin where the tattoo is

  • Dermabrasion - skin resurfacing by scraping off the epidermis using a rapidly rotating device 

  • Salabrasion - dermabrasion by salt rubbing

  • Chemical removal - what it sounds like.

  • Interestingly, some home remedies such as lemon, honey, yougurt or aloe vera can work to remove fresh, tiny. Light tattoos. That makes sense if you think about all the products that are used to remove dead skin in the beauty industry - this is almost the same thing.

  • Whichever method you chose, just make sure it’s safe.

Thank you for listening to this mini-episode of LuxeSci.  As always a big thank you to my audio engineer, DImos.  You can find us all over social media at Luxescipod.  This week share this episode with someone you know who has a tattoo.  They might find it interesting to know what their macrophages are doing. 



bottom of page