Tattoos have gone fully mainstream — nearly half of American adults aged 30 to 49 now have at least one — but the science hasn't quite caught up with the needle. Chemist John Swierk of Binghamton University puts it plainly: researchers can't yet say tattoos are definitively safe or unsafe. That doesn't mean panic, but it does mean anyone booking an appointment should know where the real risks lie.

The most common problems are short-term. Studies trying to pin down how many people develop complications range wildly, from 2% to 67%, but a Danish tattoo clinic study of a few hundred patients found bacterial infections accounted for 11% of issues and allergic reactions 37%. Infections can appear within days — redness, drainage, fever — and often need antibiotics. They can stem from contaminated equipment, bacteria on your own skin, or the ink itself. Worryingly, FDA researchers recently found bacteria in 35% of more than 200 inks tested, including some labelled sterile, and a 2012 outbreak was traced to contamination during manufacturing.

Allergies come in two flavours. Immediate reactions are often to aftercare products while skin is raw and sensitive, and usually settle with topical creams. The sneakier version shows up months or years later, and red ink is the usual culprit — you might get an itchy, raised patch inside the red petals of a rose tattoo while the green leaves stay perfectly fine. Severe cases can require laser or surgical removal of the affected pigment. Yale dermatologist Dr Christopher Bunick notes other immune reactions can cause bumps that persist for years, typically managed with corticosteroid creams.

Part of the problem is that nobody quite knows what's in the ink. In 2024, Swierk's team found 83% of tested inks contained pigments or additives not listed on the label. Europe regulates certain tattoo ink ingredients; the United States doesn't, though the FDA has issued manufacturing guidance.

Then there's the cancer question, which remains genuinely open. Some pigment migrates to the lymph nodes, and a large 2024 Swedish study led by Lund University's Christel Nielsen found tattooed people may have a somewhat higher lymphoma risk. But Nielsen stresses the baseline risk is very low and the finding doesn't prove causation — other studies on lymphoma and skin cancer have been inconclusive.

The practical takeaways are refreshingly simple. Check the area has no open sores beforehand, keep the tattoo clean and sun-protected afterwards, consider skipping red pigments if you're allergy-prone, and see a doctor if you spot infection signs or skin changes long after healing. Above all, pick an experienced artist — most known infection and allergy risks can be avoided with good technique and hygiene.

For travellers, this matters doubly: getting inked abroad means navigating unfamiliar hygiene standards and aftercare in a different climate. Whether it's a beachside studio in Bali or a booked appointment in Berlin, the same rules apply — research the artist, scrutinise the studio, and don't rush the decision just because you're on holiday.