Tattoos could help fight disease
Tattoos and medicine may seem an unlikely pair, but medical tattoos are nothing new. Religious tattoos of ancient Egyptians honored the gods and, possibly, directed divine healing to ailing body parts. Circa A.D. 150, Galen, a Greek physician working in the Roman Empire, tattooed pigment onto patients’ corneas to reduce glare and improve their eyesight. In the past century, people have tattooed their medical histories and even medical requests such as “do not resuscitate” on their wrists and chests. Modern doctors have also used tattoos to disguise scars and restore the appearance of lost body parts, such as nipples for mastectomy patients.
Today, that history comes full circle as researchers try to determine if tattooing could give health care providers a better way to administer drugs and vaccines.
It was only in 2018 that scientists figured out exactly what happens in the immune system when you get a tattoo. They identified macrophages, a type of immune cell, as critical players. Macrophages are part of the first responder unit of immune cells, also known as innate immunity. To understand what macrophages do, look no further than the Greek roots of its name: Macrophage means large eater. These pliable cells travel through the bloodstream and target microbial invaders in tissues, engulfing and “eating” them, thus clearing infections. Often, the response is so fast and effective that we don’t realize we’ve been infected at all.
Macrophages are also the accomplices that make tattoos permanent. When a tattoo needle punctures the skin, it tears apart the tissue in its path — releasing chemical distress signals that attract immune cells to the damage site and put adjacent cells on high alert. A typical tattoo will inflict hundreds of thousands, and possibly millions, of these puncture wounds. Macrophages near the tattoo site, ever on the prowl, ingest any foreign substance they find — in this case, targeting the ink the tattoo artist has applied. In a twist that researchers still don’t fully understand, the macrophage “eats” the ink but cannot destroy it.
The macrophage then does one of two things: carry the ink away to a nearby lymph node for disposal, or sit there, hunkering down with other macrophages and forming a blockade, called a granuloma, to isolate the pathogen from uninfected tissues. (The macrophage motto: “If you can’t destroy them, trap them.”) When you get a tattoo, some of your macrophages sit and hold the ink to “protect” you, in the process becoming guardians of your tattoo design.
Your tattoo design, then, is an artful, exterior display of your body’s immune response.
Tattoo artists have harnessed the body’s defense network to inscribe and preserve art within your skin. It begs the question: Why can’t researchers leverage the same approach to advance medical treatments?
In 2016, the American Academy of Dermatology estimated that 1 in 4 people in the U.S. are impacted by skin ailments such as microbial infections or cancers. Another study, in 2019, reported that Americans spend $13.8 billion battling skin and soft tissue infections each year. Physicians treat serious skin infections by giving patients intravenous or oral medication, which can be costly and can cause side effects. Minor infections may respond to topical ointments and creams, but these don’t always reach their targets.
Tattooing medications into infected tissues might work better. In a proof-of-concept study using laboratory mice with cutaneous leishmaniasis, a parasitic skin infection marked by inflamed lesions, researchers administered an anti-parasitic drug using three routes: administering it topically as a cream, injecting it into the torso with hypodermic needles (the kind widely used in health care) and using a commercial tattoo needle to inject medicine into the infection site. Tattooing treatment into the wound decreased parasite numbers and decreased lesion size and tissue inflammation more effectively than the other techniques. Researchers and pharmaceutical companies are also evaluating a similar mechanism, microneedles, for treating skin infections. Microneedle patches for common woes such as acne are already available.
Tattoos may also ease the delivery of vaccinations to prevent disease. Today, most vaccines are administered by hypodermic needles that inject into the muscle. The thicker the vaccine, the larger the needle — and often, the more painful the injection. Human skill impacts pain levels, too. An injection may hurt more if an administrator is inexperienced and doesn’t know, for instance, how much pressure to apply to the plunger. Tattooing eliminates such problems. Tattoo needles are small compared to traditional hypodermic needles, are designed to puncture the skin superficially and may also reduce human error. One research cohort has designed microneedle patches to “tattoo” a vaccine dose. Such designs, which can be stuck to the skin like a simple adhesive bandage, can eliminate administration problems created by human error.
It behooves medicine to innovate when existing techniques fail; as a tattooed immunologist myself, it seems to me that developing tattoos for medical applications just makes sense. Tattoos, research and medicine share a rich history, and the convergence of tattoos and science is a continuation of the human desire to explore and innovate — and beautify and prolong our lives.
If medicine is an art, then art too can be medicine.