#681 Why do tattoos stay in the skin forever?

Why do tattoos stay in the skin forever? Because the particles of ink are too big for the body to absorb and expel.

When you have a tattoo, the tattooist uses a needle to put ink particles into your skin. Skin has three layers, and the ink is injected into the middle layer, the dermis. The top layer of the skin is called the epidermis. Its job is to protect the inside of the body. It keeps out bacteria, germs, and anything else that wants to get into the body. New cells grow up from the bottom of the epidermis to replace the cells that die on the outside and are shed. We lose about 40,000 skin cells per hour and most house dust is made of skin cells. The epidermis is also where the color for your skin comes from, and any moles or freckles will be there. The dermis is the next layer. It is 90% of the skin’s thickness. The dermis is full of blood vessels and nerves. It makes oil for your skin, has hair follicles, and sweat glands. The bottom layer is the hypodermis, and it contains fat that acts as a cushion to protect the muscles and bones from impact. It has larger blood vessels and nerves, and it helps regulate body temperature.

A tattoo is drawn on using a tattoo machine that has a reservoir of ink and a needle. When the machine is switched on, the needle moves up and down at up to 50 times a second. The tattoo artist follows their design on the skin and the needle punctures through the epidermis and injects ink into the dermis. There is some ink also left in the epidermis, but this is passed out of the body as the old cells die and they are replaced by new cells.

So, why does the ink stay in the dermis? Every time the tattoo machine punctures the skin, it causes a wound and a regular tattoo will make tens of thousands of tiny wounds. The body senses these wounds and the immune system goes into action. The first on the scene are white blood cells called macrophages. Their job is to kill bacteria, viruses, or anything else that might have invaded the body. In this case, ink is the foreign substance, and the macrophages go to work eating the ink. Some of the smaller ink particles they are able to remove and they carry them to the lymph nodes where they can be expelled from the body. However, most of the ink particles are too large for the macrophages to remove, so they just eat them and then sit there. These ink carrying macrophages will sit there until they naturally die and then the ink will be eaten by new macrophages. This will keep going forever, holding the tattoo ink where it is in your body. As well as this, some of the tattoo ink particles will be absorbed by fibroblasts, which are the cells that make connective tissue. The same thing happens here as well. When one fibroblast dies, the ink is absorbed by another. The ink stays suspended in the dermis and never gets removed out of the skin. The ink can be seen through the epidermis and is never touched by the new skin cells that are produced above it.

Tattoos will stay there forever, but they do fade. This is usually caused by sunlight. Ultraviolet light has enough energy to break up some of the ink particles that are being held in the dermis and when that happens, they are small enough to be carried away by the macrophages. Sunlight cannot remove a tattoo because that much exposure to UV light would be extremely dangerous.

Tattoos can be removed using lasers. This is the same process that UV light causes, but on a much more controlled scale. A laser of a specific frequency is fired at the tattoo ink particles, heating them up in microseconds to the point where they explode. Once they have exploded into smaller pieces, the macrophages can go about their job of removing them from the body. Different color inks require different frequencies, which means some ink colors are more difficult to remove than others. Black is the easiest color to remove because it easily absorbs the energy, and lighter colors like white, yellow, light blue and pink are the most difficult to remove because they reflect the energy. Tattoo removal can take many months and cost far more than having the tattoo in the first place. And this is what I learned today.

Photo by cottonbro studio: https://www.pexels.com/photo/a-shirtless-tattoo-person-holding-a-key-in-front-of-a-motorbike-5235789/

Sources

https://www.drdoppelt.com/tattoos-whats-happening-under-your-skin/

https://www.immunology.org/public-information/bitesized-immunology/cells/macrophages

https://www.zmescience.com/science/biology/why-tattoos-are-permanent-0554/