Before you get a butterfly stamped on your back, take heed: Tattoo inks can cause rashes, infections, and inflammation, and doctors still aren’t sure how the inks’ chemicals—which eventually migrate into the lymph nodes—behave in the long term. A chemical in black inks called benzo(a)pyrene, for example, has caused skin cancer in lab animals, and malignant melanomas have, on occasion, been discovered in tattoos, the San Francisco Chronicle reports. That may be coincidence, but the FDA has decided that with 45 million tattoo-adorned Americans, the topic is worth a look.
Some 36% of late-twentysomethings have tattoos, but most don’t think much about health issues, artists say; instead, they’re worried about the long-term appearance of the image. But scientists recently found another chemical in 14 different black inks that has been associated with abnormal sexual development in infants—but whether it's also bad news for the tattooed remains unknown. "While this is a potential source of high exposure, it might not last very long and may not present a risk to health," says a Harvard epidemiologist. Thus far, the FDA hasn’t cited any issues worrying enough to prompt restrictions—but recently the agency has launched studies focused on the inks.