When thinking in terms of possible side effects from tattoos, most people think of skin infections, irritation, or even allergic reactions. But there's another little known problem with tattoos: Studies have shown that in rare cases, they can cause skin burns when a person is undergoing an MRI scan.

“What you have to understand is that while this is a known and documented side effect, not very many people have had these problems,” explains one radiologist from Bengaluru’s Vydehi Hospital.

The ink used in some tattoos may contain certain metallic elements. On exposure to the Magnetic Resonance Imaging (MRI) machine, these elements are “activated” and heat up, which may then cause the skin to burn. In one study, researchers observed that the ink pigment moved slightly on the skin when exposed to a horseshoe magnet. On further research on the pigments used in tattoo inks, they found a few elements that exhibited “magnetic properties.” Iron oxide containing pigments (commonly found in black or brown ink) moved on exposure to a magnetic field while pigments which contained titanium, copper, and carbon did not.

“We usually make our patients undergo screening for any metal before they are taken up for an MRI. The MRI machine is essentially a large donut-shaped magnet. So if someone has any piercings or implants, we need to know prior to taking them into the room. For this we ask a few simple questions and take a metal detector to scan the patient,” explains the radiologist. She adds that in some cases, people are screened using alternative means if it is found that someone is unable to undergo the scan for any reason.

Two researchers, Kanal and Shellock, who were among the first to study this effect, it's recommended that doctors place an ice pack or cold compress over the tattoo before exposure to an MRI scan, and to leave it in place until the scan is done. They also stated that applying pressure to the tattooed area prevented tissue from moving around. Subsequent studies proved that those with cosmetic tattoos, such as eyeliner or eyebrows, were also at risk of developing skin burns.

It was also theorized that these metallic elements would form an electric current at a much higher degree of heat than the skin was capable of withstanding, and would cause a superficial burn.

Doctors are recommended to ensure that all patients who require an MRI were asked to undergo some basic screenings, and to give patients a questionnaire prior to undergoing an MRI.

I have a tattoo and need an MRI. Should I be worried?

While skin burning has been noted in a few, rare circumstances, doctors recommend that you notify the doctor or technician of any tattoos prior to the scan, according to several radiologists. Many also added that it was just a precautionary measure, so that if any reactions occurred, they could intervene immediately.

However as another radiologist from Vydehi Hospital, Dr Sheetal Reddy, tells us this is not always necessary. "Maybe it exists in theory, but in practice it must be a very rare instance, so most people don't have to worry."