If you're among the many who have woken up disoriented, hungover, and sporting a fresh tattoo, here's one more thing to worry about: that body art may cause a skin reaction that can last for months, even years.

Dr. Marie Leger, a dermatologist and assistant professor at the New York University, has treated patients with such skin problems. She became curious about the frequency of tattoo reactions, so decided to hit the streets and gather some data.

"I've taken care of patients who have had problems with their tattoos and was curious about how common this was," said Dr. Leger. "I was surprised at the results."

She chose a likely locale: New York's Central Park, where folks from every walk of life can be observed in their natural habitat, either strolling among the trees, lounging on the greens, or passed out on a bench. And fortunately for the good doctor, tattoos were in abundance.

Leger and her colleagues interviewed 300 randomly selected people (149 men, 151 women), the sole criteria being they sported ink. Subjects were asked about any unusual symptoms, outside the normal skin reactions that occur as the tattoo heals. And what the scientists found was that 4 percent complained of a short duration rash following the procedure, while an additional 6 percent reported skin problems lasting longer than four months.

Most of the complaints were of skin that became "itchy, scaly, raised, and/or filled with edema."

"The colored portion can sometimes raise up as much as a centimeter above the skin and can affect the texture of the skin and the way the tattoo looks," Leger explained.

And what might be causing such nasty skin reactions? Leger believes allergies are to blame.

Almost two-thirds of the people complaining of long-lasting rashes also reported having allergies, compared to only one-third of those who denied any negative reaction following the procedure.

But for people who know tattoos, the news was hardly surprising.

Mike Martin, president of the Alliance of Professional Tattooists, said, "I don't have any statistics or percentages of people who break out with a rash and can speak from my personal experience only. The prevalence of a rash appearing is uncommon although not unheard of throughout the tattoo industry. Some folks' bodies do not like red pigments."

And sometimes rashes occur long after the procedure.

"I have heard of the rash appearing 12 months after the tattoo has been healed," he added. "It is usually in the site where red pigments were tattooed into the skin. The rash persists until all of the red ink has been pushed from the skin. Occasionally, I have seen this happen to some blues, purples and greens that were tattooed on someone overseas."

So Dr. Leger provides a few pointers, for those already inked or folks contemplating a tat. First and most important, pick a reputable parlor, one that follows state health guidelines. Since many rashes seem tied to red ink, perhaps choose a different color for your body art. And finally, follow the directions for after-care, including keeping the site clean and avoiding the sun.

And remember, there's always laser removal.