But even smaller tattoos done with black ink can take multiple years to erase, researchers found.

Of 352 people getting a tattoo removed with the so-called Q-switched laser, just under half had their ink successfully eliminated after 10 sessions, and three-quarters after 15 sessions, in research from Italy.

Smokers, as well as people who had their treatment sessions less than two months apart, were less likely than others to see their body art disappear.

About half of young people who get a tattoo ultimately choose to have it removed, the researchers wrote. During those procedures, laser pulses are used to break up tattoo ink, and the tiny ink particles are then removed by immune cells.

Dr. Luigi Naldi, from Centro Studi GISED in Bergamo, Italy, said that because of the laser's reaction with the individual pigments, yellow and blue inks may change color but not disappear with treatment.

That's not a big surprise, he told Reuters Health, but people with those colorful tattoos "should be aware that removal of this tattoo may be more difficult and may not be satisfactory."

The effect of smoking is a newer and more interesting finding, and could be explained by smoking's impact on the immune system, said Naldi, who worked on the study.

"It affects the function of cells in the body which are in charge of removing the remaining (ink) material," after it is broken up by the laser, he said.

QUICKER PULSES, FASTER CLEARANCE

In another study published alongside Naldi's in the Archives of Dermatology, U.S. researchers tested a new laser device for tattoo removal involving a shorter pulse - lasting a picosecond, versus the traditional nanosecond.

"With laser treatment for tattoos, no big changes have come about in the past 20 years," said Dr. Nazanin Saedi, the lead author of that study from Thomas Jefferson University in Philadelphia.

Using the Q-switched laser, she said, "Patients need so many treatments in order to clear their tattoo."

The sessions usually cost at least a couple of hundred dollars each.

For her study, 12 out of 15 patients completed at least two tattoo removal sessions with the picosecond laser. All 12 had their ink at least 75 percent cleared and were "satisfied" or "extremely satisfied" with the outcome, most after two to four treatments.

The research was done at SkinCare Physicians in Chestnut Hill, Massachusetts.

Saedi said the company that makes the new device and partially funded her study, Cynosure, is doing clinical trials in hopes of getting the laser approved by the Food and Drug Administration.

But for now, the new treatment isn't available outside of studies, Saedi told Reuters Health.

One dermatologist not involved in the new research agreed that the number of sessions required for tattoo removal is a deterrent for many.

"The number of people getting tattoos continues to increase… which means, when you look at people 10 to 20 years after that, the number of people seeking removal of that tattoo is also higher," said Dr. David Goldberg, head of laser research in the dermatology department at the Mount Sinai School of Medicine in New York.

But, he told Reuters Health, "the number of people who complete removal of their tattoos is very small… and that's in part because so many sessions are required."

Goldberg said there are still limitations to picosecond lasers, including that the machines break down frequently and are very expensive. But he thinks that within the next few years, the new lasers will "transform" how tattoo removal is done.

For now, he said, people considering getting a tattoo should take the decision very seriously.

"It takes about a half hour to an hour to get a tattoo, but it can take years to get it removed," Goldberg said.

SOURCES: and Archives of Dermatology, online September 17, 2012.

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