SciTech

Tattoos are inflammations

Credit: Michelle  Wan /Art Editor Credit: Michelle Wan /Art Editor

If you’re thinking about getting a tattoo, you might want to learn about the science behind the art before you make your final decision. While on the outside, a tattoo is a beautiful and symbolic creation, on the inside, it is actually the result of a perpetual inflammatory process.

Tattoos have been used as a form of self-expression for millennia. According to neuroscientist Claudia Aguirre in a TED-Ed video titled “What makes tattoos permanent?”, the earliest evidence of body ink was found on a Peruvian mummy from 6,000 BCE. To add even more history to this tradition, the tattoo machine was invented in the late 1800s, its design based on Thomas Edison’s engraving machine.

Today, one look around campus can reveal a variety of different tattoo designs, colors, and types of people sporting them. With the independence of life at college, who’s to stop you from getting one, too?

Maybe all you care about is whether or not it will hurt, but there is a lot more that can be learned about the tattooing process. Although humans shed 40,000 skin cells per hour, the TED-Ed video explains that tattoos remain permanent because they are not on the epidermis, but rather inside a second layer of skin: the dermis.

A tattoo machine punctures the skin continuously with a needle, depositing ink into the dermis, which is made up of collagen fibers, nerves, glands, blood vessels, and more.

Whenever the needle penetrates the skin — which could be up to 3,000 times per minute — it causes a wound which alerts the body to begin an inflammatory war to fight the intruding tattoo ink. White blood cells known as lymphocytes form the first line of defense; however, most of the pigmentation particles are too large for them to fight. Next, a different type of white blood cell — macrophages — come in and eat up the pigmentation particles. Some of these macrophages will carry the dye back to the lymph nodes, but many will simply remain in the dermis — dye and all — forever suspending your angel wings, Chinese character, or lover’s name in the second layer of skin.

In addition to existing inside macrophages, some ink particles simply float eternally in the gel-like matrix of the dermis. Still, others are eaten by dermal cells called fibroblasts, which remain in the dermis for their entire life cycles. Even when fibroblasts die, they get taken up by new dermal cells which hold both the old cell and the dye within it.

How, then, can tattoos be removed? According to Anne Laumann, professor of dermatology at Northwestern University, the best method of tattoo removal is laser treatment. In laser treatment, light targets a specific color and breaks up the ink particles of that color. By breaking up the ink particles, laser treatment creates particles that are small enough to be carried away by white blood cells. Unfortunately, this method does not always remove the entire tattoo.

Besides the tattooing process and tattoo removal, there is also a science to the ink used for tattoos. Traditional pigments were made from ground up minerals and carbon black, but today’s pigments can sometimes also include industrial organic pigments, vegetable-based pigments, or plastic-based pigments.

While the composition of your tattoo ink will inherently vary based on where you get your tattoo done, there are common compositions for various colors of ink. For example, black ink often includes carbon, logwood, or iron oxide; brown contains ochre; red has cinnabar (HgS) or cadmium red (CdSe), which are both known for toxicity. Consequently, it would be in your best interest to ask your tattoo artist about the chemicals they use in their inks to avoid allergic reactions or phototoxic reactions.

It has often been said that science is an art, but the biological and chemical intricacies behind tattoos suggests that art is a science, too.