Whether you consider it art or mutilation, body piercing has become extremely popular, especially among the young.
However, bold self-expression isn't without risk: A recent survey of college students in New York found that almost one in five who get pierced will suffer from a medical problem.
Bleeding, tearing and infection
The numbers suggest that four million people across America may encounter bleeding, tearing or infections, says study author Dr Lester Mayers of Pace University's Division of Sports Medicine.
"Even if a small percentage require antibiotics, drainage procedures and physician visits, you're talking a significant medical cost," he notes.
All age levels had piercings.
The survey of 454 students, apparently the first of its kind, also found 60 percent of female students had one or more piercings in places other than their earlobes. Forty-two percent of males had piercings in their earlobes and elsewhere.
College students of all age levels had piercings.
"It's not a passing fad that was done by a lot of kids for one year or two years," Mayers says. "It seems to be fairly constant."
The findings appear in the January issue of Mayo Clinic Proceedings.
Belly ring the most popular
For women, the most common pierced body part was the navel (29 percent), followed by the ear outside of the earlobe (27 percent), the tongue (12 percent) and the nipple (five percent).
Piercings that were removed are not included in those numbers.
For men, the most popular piercing site was the ear and ear lobe (31 percent), followed by the tongue (two percent).
Men and women were least likely to pierce their genitals, eyebrows and lips. Only a dozen of those piercings were reported.
Infection occurred after 17 percent of piercings. By contrast, the 23 percent of students with tattoos reported no cases of medical problems.
Belly button most common source of infection
Mayers says he was inspired to launch the study after noticing many Pace University athletes were adorned with body art and jewellery. He checked medical journals and found few studies about piercing and tattoos, although there were isolated reports about individual problems.
"We just decided it would be a good idea to find out how common these practices are," he says.
The medical problems were generally not serious, although they caused some people to remove their jewellery, he says. The belly button was the most common site of infection.
"The navel takes a long time to heal -- six to nine months -- and is intrinsically a rather dirty spot bacterially," he says.
Navel infections are indeed common, says Dr Jay Goldman, national director of ambulance and emergency medical services with the Kaiser Permanente Health Plan. "They're not serious, but they're annoying, and they hurt," he says.
Goldman has also seen many ear infections.
"I see lots of earrings that have been lost in the earlobe and have to be pulled out," he says. "I see earlobes that are split by heavy earrings, or improperly pierced ear holes or too many ear holes."
Diseases can also be spread
Piercing or tattooing can also spread blood borne diseases such as hepatitis and HIV.
The causes of piercing-related infections aren't always clear.
"It's hard to know if it's because the person didn't take proper care of the pierced area or because an improper technique was used," says Dr Charles Simmons, an emergency room doctor with Scripps Mercy Hospital in San Diego.
However, experts agree the medical problems can largely be prevented through cleanliness and the use of experienced, qualified body artists.
While the study didn't ask why students got pierced or tattooed, Mayers has some theories. It is not, he says, a form of rebellion, nor a product of a quick or drunken decision.
"They're not out to get mom or dad all angry," he says. "It seems to be a very personal identity statement."