If the cells of our skin are replaced regularly, why do scars and tattoos persist indefinitely?

Join Our Community of Science Lovers!

The public information office of the Dermatology Associates of Atlanta provides this brief reply:

"The answer is really quite simple. The cells in the superficial or upper layers of skin, known as the epidermis, are constantly replacing themselves. This process of renewal is basically exfoliation (shedding) of the epidermis. But the deeper layers of skin, called the dermis, do not go through this cellular turnover and so do not replace themselves. Thus, foreign bodies, such as tattoo dyes, implanted in the dermis will remain."

James B. Bridenstine of the department of dermatology at the University of Pittsburgh Medical Center adds:

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

"Our skin is primarily made of the protein collagen, which is produced by cells known as fibroblasts. When the skin (or any other tissue, for that matter) is wounded, the wound-healing process initiates the generation of new fibroblasts to produce scar collagen, which is different from the collagen in normal skin. Even though individual cells within the skin periodically die and are replaced with new cells, the scar collagen remains. The only time when wounds will heal without producing scars is during the fetal stage of life, when the skin produces fetal collagen, a protein that is different from adult collagen. If we could find a way to turn on the production of fetal collagen after birth, then we could, presumably, perform scarless surgery.

"Tattoos remain in the skin because the ink particles that produce the coloration are too large to be ingested by the white bloods cells that patrol the body and carry foreign bodies away from the skin. The new tattoo-removing lasers work because the laser energy pulverizes the ink into microfine dust particles that are small enough to be taken in by the white blood cells and carried away.

It’s Time to Stand Up for Science

If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.

I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.

If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.

In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.

There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.

Thank you,

David M. Ewalt, Editor in Chief, Scientific American