Paul Roe, owner of Britishink Tattoo, tells us what you should know before you get inked. From the type of pigment to the equipment your artist uses, Roe, these are the steps of tattooing. (Ben Dorger/The Washington Post)

Tattoos seem more popular than ever, but is that artistic ink dangerous to your health? Little attention has been paid to that question, even as rates of skin cancer — the most common cancer — have been steadily growing.

German dermatologists published an article in March about their effort to determine if a tattoo had caused skin cancer in a 48-year-old man. About four months after a tattooist had pumped red and black pigments into the skin on the man’s left leg, he was diagnosed with skin cancer at a spot where red ink had been used, and he was sent to the specialists for treatment.

In the article — it appeared in PRS Global Open, a medical journal of the American Society of Plastic Surgeons — the dermatologists reported finding no direct connection between the tattoo ink and the cancer, but they urged doctors to look for signs of squamous-cell carcinoma in patients who have a reaction to tattoos.

They also pointed out that there are no international standards for tattoo ink mixtures and that inks in some countries may contain carcinogenic substances, giving tattoo-seekers a lot more to think about than whether the needle is sterile and the artist is talented.

An earlier review also found no clear link to cancer, saying, “The number of skin cancers arising in tattoos is seemingly low, and this association has to be considered thus far as coincidental.” But the authors also said that tattoo ink may contain possible carcinogens, that it remains in the skin for a lifetime and that the long-term effects are unclear.

Many countries regulate the inks as cosmetics. In the United States, the Food and Drug Administration has the authority to screen the pigments used in inks before they go on the market, but the agency says it usually does not do so “because of other competing public health priorities and a previous lack of evidence of safety problems specifically associated with these pigments.”

Cosmetics in general do not require approval before they reach the market. Instead, the FDA investigates when it receives complaints about products.

“FDA has basically been acting once cosmetics reach the market and cause harm,” said Janet Nudelman, director of the California-based Campaign for Safe Cosmetics, who has criticized the FDA regarding lead in lipstick and who says tattoo ink should be examined even before complaints are filed.

The potential for problems with inks was illustrated in 2012, when the FDA reported an outbreak of skin infections associated with tattoos. It determined that ink had probably been contaminated during manufacturing, either because of unsanitary processes or contaminated ingredients.

The Centers for Disease Control and Prevention reported 22 confirmed infections in the states of New York, Washington, Iowa and Colorado.

The two companies connected to those infections, Catfish Carl’s in Arizona and another that the FDA has not named publicly, voluntarily recalled the inks from the market, according to Juli Putnam, an FDA spokeswoman.

Over the summer, White and Blue Lion, a California company, recalled its ink after the FDA found that contamination of ink in a home-tattoo kit had led to a skin infection in one person.

Almost all tattoo inks, dermatologists say, contain chemicals that can cause allergic and other reactions. People such as Chris Andersen of the Miami Heat may consider that a risk they’re willing to accept. (Mike Ehrmann/Getty Images)

“Even if a person receives a tattoo at a tattoo parlor that maintains the highest standards of hygienic practice,” the FDA warns, “there remains a risk of infection from the use of contaminated ink.” Medical attention should be sought if a tattoo becomes painful or develops redness, swelling or blemishes, the FDA advises.

The FDA, which says there have been no in-depth studies of the inks, is researching the chemical composition of tattoo ink and its safety at the National Center for Toxicological Research in Arkansas.

Almost all inks, dermatologists say, contain chemicals that can cause allergic and other reactions. They also warn that tattoos can cover up signs of skin cancer such as moles and that some colors can be more irritating than others.

“In scientific literature, it is not an unknown phenomenon that red ink causes skin irritation or even worse,” Felix Julian Paprottka, one of the doctors involved in the German case, said.

Michi Shinohara, a dermatologist and clinical assistant professor at the University of Washington in Seattle, says she has seen patients with tattoo reactions that mimicked skin cancer.

“Sometimes these actually have to be treated as skin cancer because we can’t tell for sure,” she says.

That leaves doctors looking for answers. “The reported few cases are considered to be mere coincidences, since skin cancer is very common,” says Jorgen Serup, a dermatology professor at Copenhagen’s Bispebjerg University Hospital, which has a clinic that treats tattoo problems and researches safe practices.

“Cancer may easily occur in tattooed skin independent of the ink or pigment. . . . However, we cannot completely deny it may happen,” added Serup, who has published extensively on industrial pigments, skin and tattoo complications.

The Copenhagen clinic warns patients that no tattoo ink should be considered entirely safe. “Inks are industrial products with generally unknown content,” the clinic says in a fact sheet.

The clinic also urges those getting a tattoo to keep a record of the ink used, its manufacturer and other details, in case problems develop.

Lack of international standards, the German doctors say, complicates ensuring safety because problems reported in, for example, Europe may not be picked up elsewhere even though some inks are distributed globally. Every week, the European Commission gathers information from its member countries about dangerous products and sends out warnings through its Rapid Alert System for Non-Food Products, or Rapex.

The reports, which are shared among the 28 EU member states and other participating countries, are based on tests carried out by each country’s cosmetics regulatory authorities. Since 2009, EU members have identified more than 20 inks from the United States as dangerous and banned their sale. Those products can be found in a search of the Rapex site.

Some of the blacklisted inks, according to Rapex recall reports, contained potential carcinogens, toxic substances and nickel, cadmium and arsenic.

In the United States, regulation of tattoo parlors and tattoo artists is left to state and local jurisdictions.

“Because the FDA cannot require a cosmetics company to submit data before marketing a product or require a company to tell the FDA when they receive a report that one of its products has caused an adverse reaction in a user, the FDA may not know when there are problems,” Putnam, an FDA spokesman, says.

The FDA urges health-care providers, public health officials, tattoo shop owners, tattooists and consumers to report tattoo-ink-related health complications through the agency’s MedWatch program.

Founded in 1993, MedWatch is a reporting system for adverse reactions to cosmetics, drugs, medical devices, dietary supplements, medical foods and infant formulas. The federal agency investigates the complaints and, if they are confirmed, issues safety alerts and orders product recalls, withdrawals or labeling changes to protect the public health.

Some tattooists shrug off the possibility of problems with ink.

“Most researchers use mouse skin [in experiments], and their findings may not accurately apply to humans,” says Paul Roe, the owner of Britishink Tattoo Studio on H Street in Northeast.

Tats may be cool, but many questions about them remain unanswered.

Misiko, from Nairobi, wrote this article during his fellowship in the Alfred Friendly Press Partners program, which places international journalists at American newspapers.