Tattoos are often merely decoration, but for cancer patients they can be a lifesaving tool. Now scientists say the tattoos will be easier on patients: A study in the journal ACS Nano says a new ink formula for medical tattoos will cause fewer side effects and will physically look better when used as guides for doctors.

“Tattooing has been utilized by the medical community for precisely demarcating anatomic landmarks,” the study says. “This practice is especially important for identifying biopsy sites of nonmelanoma skin cancer due to the long interval (i.e., up to 3 months) between the initial diagnostic biopsy and surgical treatment.”

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When doctors use current inks to mark the spot, they can cause inflammation and discomfort, according to a statement from the nonprofit organization American Chemical Society. Adding to the problem, the tattoos leave permanent coloring on the skin; post-treatment patients may need surgery or laser removal if they want them gone.

The lingering marks can be an unwelcome reminder of a difficult period in a person's life.

But the new ink is easier to tolerate because it “glows only under certain light conditions and can disappear altogether after a period of time,” the ACS says. That light is a wavelength of 465 nanometers, which is in the indigo and blue range of the visible light spectrum. “Doctors would be able to use a special light to see the dye.”

When the researchers tested the ink in mice, they found that the nanoparticles they used did not cause inflammation and lasted for three months, the typical period for certain skin cancer patients between their biopsy confirming the cancer and their treatment.

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