More and more teens are opting to pierce their upper ears, but the procedure is much riskier than many think, according to a new report.

Piercing upper ear cartilage is much riskier than ear lobe piercing and can lead to serious infection and permanent disfigurement, according to research presented at a meeting of the Infectious Diseases Society of America Thursday in Chicago.

"Kids don't seem to realize that ear piercing is, in its own small way, an invasive procedure, and until it heals, any pierced body part is at risk for infection," said William Keene, an epidemiologist at the Oregon Department of Human Services Acute and Communicable Disease Program in Portland.

Infections can cause the ear cartilage to erode, causing the outer ear tissue to sag and lose its normal shape. Cartilage also takes longer to heal because there is less blood circulation than in the lobe. Signs of infection include pain, tenderness, redness and drainage of pus or blood at the piercing site.

Keene led an investigation into an outbreak of ear-piercing related infections that occurred in Klamath Falls, Ore., in the summer of 2000.

The outbreak first came to light when an ear, nose and throat specialist called the local health department to report seeing two teenage patients a few days apart. Both had nasty infections on the upper ear, and both reported getting their ears pierced at the same local shopping mall kiosk.

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Upon further research, health investigators found that seven of 53 people who had their upper ear cartilage pierced at the kiosk in a six-week period had similar serious infections. People with infections were between the ages of 10 and 19, and two were male and five were female.

"Some of these kids ended up with quite serious cosmetic problems," Keene said. Three later had reconstructive surgery to repair their deformities.

All seven developed auricular chondritis -- cartilage infection of the outer ear -- within three days of having their ears pierced. Four were hospitalized: one to receive intravenous antibiotics, two to undergo incision and drainage of an abscess that formed at the site of the piercing, and one for both reasons.

At the jewelry shop that was the source of the outbreak, both lobe and cartilage piercings were being done with a spring-loaded "gun," which shoots a flat-ended stud through the ear tissue.

The guns are not recommended for cartilage piercing. In some states that try to regulate the industry, including Oregon, guns are not legal for cartilage piercing. The shock of gun piercing is much more traumatic in cartilage than in the ear lobe, Keene said.

"It's a cautionary tale," he said. "Obviously the safest thing to do is not to get pierced at all. But if you are determined to have your upper ear pierced, be sure the operator uses a disposable needle, not a gun, and be sure that he or she practices good hygiene and technique. Admittedly, it can be difficult for the consumer to really be assured of that."

About 30 states have some kind of legislation regulating sanitation and hygiene of businesses that perform body piercing, according to the Association of Professional Piercers, but enforcement often is lax.