Getting inked is a big decision. You have to consider placement and selection of a lifelong embellishment. And you have to worry about things like allergic reactions and infection during the tattooing process. Now, ink fans have one more thing to worry about: Skin cancer—the most common form of cancer in the U.S.

Do tattoos cause skin cancer? Not exactly. But they can make it tougher to detect it. And the longer it is before you discover you have a problem, the tougher it is to treat successfully.

When tattoos are placed over moles, they can make it tougher to detect changes in those moles. It’s typically changes in a mole’s appearance that can clue you in to a cancer risk.

Tattoos can also cause a skin reaction that creates a bump similar to a type of skin cancer called squamous cell carcinoma. Those bumps are difficult to distinguish from skin cancer, and can lead to unnecessary skin cancer fears—and even treatments.

One in 5 Americans will develop skin cancer in their lifetime—that’s more than 62 million people. Considering just shy of 1 in 5 Americans have at least one tattoo, it’s easy to see how the intersection of frequency with risk can spell trouble.