How are 'traumatic tattoos' made, and do you have one?

Usually, we get tattoos on purpose. But some injuries leave us with a different type of mark known as a "traumatic tattoo" — and these tattoos have nothing to do with needles or ink. So what exactly are traumatic tattoos?

Traumatic tattoos are formed when everyday materials, like graphite, dirt or gravel; or metal pieces, like shrapnel, become lodged beneath our skin, leaving a visible (and often long-lasting) mark.

"It's when foreign particles like dirt, asphalt, metal, sand, etc become embedded into the skin's … dermis," Dr. Mara Weinstein Velez, a dermatologist at the University of Rochester Medical Center, told Live Science in an email. "And it happens more often than you'd think! Events like car accidents, scrapes and falls can cause this."

These residual marks don't always cause pain or even discomfort in the long term, but their appearances can last a lifetime. While some are born from truly traumatic events, like a motorcycle crash that ends in road rash, leaving gravel or asphalt trapped under the skin, or a gunshot wound that isn't fully cleaned, others originate from common experiences, like the poke of a pencil in an elementary school classroom.

Sometimes the material itself becomes unlodged naturally over time, and sometimes it travels nearby within the body. For instance, one child had a pencil lead in their hand travel to their wrist. But in these cases, particles sometimes remain at the original entry spot, which is why a dark-colored scar can be left behind, under the skin.

Although the presence of an old traumatic tattoo isn't necessarily harmful or worthy of a trip to the doctor on its own, experts say it's best to seek medical advice when you're first wounded. The biggest risk is usually the possibility of infection, as harmful bacteria can enter the body along with the foreign object. However, surgery may also become necessary if the object has migrated under the skin to a more risk-prone location or if it has become uncomfortable. Always consult a doctor if you experience this type of injury.

"It's very important to seek medical help right away to avoid infection, since it is a foreign object," Weinstein Velez said. "Treatments like minor surgeries, laser and dermabrasion can help safely remove the foreign matter from the skin."

People who work in physically demanding industries, like mining and construction, are more likely to develop traumatic tattoos in the workplace, as they're exposed to fast-moving foreign materials like silt and rock more often during their day-to-day life.

But the traumatic tattoos we're perhaps more familiar with are small, barely noticeable scars from pencils. Pencils are made with graphite, which is a soft mineral held together with clay and wax, and is considered nontoxic and safe. However, "a doctor will probably need to see deep stab wounds that go further than the skin and any that are close to the eyes," according to Missouri Poison Control.

Traumatic tattoos also appear frequently in the military, often from the enmeshment of gunpowder and ammunition under service members' skin after explosions or gunshots — and even during weapon malfunctions during live drills, as seen in one study conducted by researchers with the Department of Oral and Maxillofacial Surgery at the Womack Army Medical Center in North Carolina.

Even if not otherwise treated, traumatic tattoos can be addressed from a cosmetic standpoint. To disguise or cover these marks, dermatologists employ the same types of lasers that are typically used to remove professional tattoos, matching the color of the trapped pigment to the appropriate wavelength of light. The pigment fragments into smaller pieces when targeted by these lasers. However, because some tattoo colors are able to absorb a wider range of wavelengths than others, meaning they can be broken into even smaller particles that the immune system can then target, dermatologists use different tools on different marks depending on color and placement.

The laser "breaks up the pigment, and then your body's immune cells, called macrophages, clear out the pigments," said Dr. Anna A. Bar, a professor of dermatology and co-director of Mohs micrographic surgery at Oregon Health and Science University. "It's not an instant result — you have to wait like a month for the tattoo to fade."

Even though a traumatic tattoo may take time and multiple sessions to address, because there is usually less pigment involved, "they're often easier to remove than professional tattoos," she added. "Usually, it's a bit easier to remove amateur tattoos or traumatic tattoos."