FRIDAY, March 8 (HealthDay News) -- Women who use petroleum jelly vaginally may put themselves at risk of a common infection called bacterial vaginosis, a small study suggests.

Prior studies have linked douching to ill effects, including bacterial vaginosis, and an increased risk of sexually transmitted diseases and pelvic inflammatory disease. But little research has been conducted on the possible effects of other products some women use vaginally, said Joelle Brown, a researcher at the University of California, San Francisco, who led the new study.

She and her colleagues found that of 141 Los Angeles women they studied, half said they'd used some type of over-the-counter product vaginally in the past month, including sexual lubricants, petroleum jelly and baby oil. Almost as many, 45 percent, reported douching.

When the researchers tested the women for infections, they found that those who'd used petroleum jelly in the past month were more than twice as likely as non-users to have bacterial vaginosis.

Bacterial vaginosis occurs when the normal balance between "good" and "bad" bacteria in the vagina is disrupted. The symptoms include discharge, pain, itching or burning -- but most women have no symptoms, and the infection usually causes no long-term problems.

Still, bacterial vaginosis can make women more vulnerable to sexually transmitted diseases, including HIV. It also sometimes leads to pelvic inflammatory disease, which can cause infertility.

The new findings, reported in the April issue of Obstetrics & Gynecology, do not prove that petroleum jelly directly increased women's risk of bacterial vaginosis.

But it's possible, said Dr. Sten Vermund, director of the Institute for Global Health at Vanderbilt University School of Medicine in Nashville, Tenn.

Petroleum jelly might promote the growth of bad bacteria because of its "alkaline properties," explained Vermund, who was not involved in the study.

"An acidic vaginal environment is what protects women from colonization from abnormal organisms," Vermund said.

He noted that many studies have now linked douching to an increased risk of vaginal infections. And that may be because the practice "disrupts the natural vaginal ecology," Vermund said.

Normally, the vagina predominantly contains "good" bacteria that produce hydrogen peroxide. And experts say that this natural environment "cleans" the vagina; women do not need special products to do it.

Yet many women continue to douche, using products that may contain irritating antiseptics and fragrances. Up to 40 percent of U.S. women aged 18 to 44 douche regularly, according to the U.S. Department of Health and Human Services.

"The frequency with which American women use unnecessary and harmful intravaginal products is unfortunate," Vermund said.

It's not certain that douching, itself, causes infections, but the American College of Obstetricians and Gynecologists advises women against the practice.

The current findings are based on a group of racially diverse women who agreed to screening for sexually transmitted diseases. Slightly more than one-quarter were HIV-positive.

Overall, Brown's team found, 21 percent of the women had bacterial vaginosis, and 6 percent had a yeast infection. Women who'd used petroleum jelly in the past month were 2.2 times more likely to have bacterial vaginosis than non-users. That was with other factors, including race, age and douching habits, taken into account.

It did not appear that women were using the product because of symptoms. Women with the infection were no more likely to report vaginal symptoms than other women were. And none of those with symptoms said they used petroleum jelly for relief.

In contrast to those findings, douching was not linked to bacterial vaginosis risk in the study.

Brown said this could be the result of having only a small number of women in the study "and the fact that women used various substances for intravaginal washing -- which undoubtedly varied substantially in their chemical constituents and concentrations."

Similarly, sexual lubricants were not linked to increased odds of bacterial vaginosis. That finding echoes what past studies have found, Vermund said, so women who need sexual lubricants for comfort can take some reassurance, he noted.

Still, Brown said that larger studies are needed to confirm these findings, and to understand how various products can affect women's health if they are used vaginally.

For now, she recommended that women ask questions before using any product vaginally. "Women should talk with their health care providers and ask them if the products they are using inside their vagina are known to be safe for use in the vagina," Brown said.

More information

The U.S. National Library of Medicine has more information on vaginal diseases.