Those mundane yeast and bacterial infections, and the inserted products themselves, can damage vaginal tissue and raise a woman's susceptibility to sexually transmitted diseases, such as herpes, chlamydia and HIV, researchers said.
"Women are clearly doing harm to themselves, by using the vast majority of what's out there on the shelves and following the advice of mothers and friends," said Dr. Michael Zinaman, chair of obstetrics and gynecology at St. Elizabeth's Medical Center in Boston, who was not involved in the study.
Brown's team recruited 141 women in Los Angeles who agreed to answer questionnaires about their product use and undergo lab tests for vaginal infections at the study's outset and one year later.
The researchers found that 66 percent of women reported washing, douching or inserting commercial lubricants or other over the counter products - other than tampons - in the previous month.
Among the women who used products intravaginally, 45 percent used washes including commercial versions or vinegar-and-water mixtures, for example.
The most commonly employed products were sexual lubricants: 70 percent of the product-using group used commercial lubricants, while 17 percent reported using petroleum jelly and 13 percent used oils.
Based on lab tests, the women who used products not intended for vaginal insertion, such as oils and Vaseline, were more likely to have yeast and bacterial infections according to the findings published in the journal Obstetrics & Gynecology.
For instance, 40 percent of the women who used petroleum jelly as a vaginal lubricant had bacterial vaginosis - an infection that can be caused by a number of common bacterial species - compared to 18 percent of women who did not insert petroleum jelly.
And 44 percent of women who reported using intravaginal oils tested positive for Candida, the fungus that causes yeast infections, compared to 5 percent of women who did not use oils.
Researchers suggested the increased risk for these common infections might result from the products upsetting internal pH and beneficial microbe communities, allowing harmful organisms to proliferate.
Normally, the vagina is home to a finely tuned system of good and bad bacteria, which produce acids that protect against infections and viruses.
Bacterial vaginosis is usually caused by an imbalance in the normal bacteria populations, according to the Centers for Disease Control and Prevention. Most women report no symptoms, but some have abnormal discharge or odor.
Doctors do not recommend that women use douches or vaginal washes because they can alter the balance of bacteria and don't seem to offer any benefit.
The natural balance of bacteria in the vagina is an "Evolutionary protection that is just washed away," with soaps, perfumes or douches, according to Zinaman.
A representative for Vaseline manufacturer Unilever told Reuters Health by email, "Vaseline Petroleum Jelly is for external use only, and we state this on our packaging for consumers. We do not recommend Vaseline Petroleum Jelly be used as a vaginal lubricant and have not performed any testing to support this use. Vaseline petroleum jelly should also not be used as a sexual lubricant in combination with latex barrier protection, as it can degrade the latex."
Doctors have always advised against using petroleum jelly intravaginally, according to David Katz, a professor of biomedical engineering and of obstetrics and gynecology at Duke University in Durham, North Carolina.
The study did not determine why petroleum jelly might promote bacterial vaginosis. Petroleum-based products suck water out of the surfaces they contact, and could make the sensitive skin of the vagina more prone to infection, said Katz, who was not involved in the new study.
It is also possible, Brown's team cautions in their report, that at least some of the women using petroleum jelly internally were trying to ease symptoms of vaginosis. The study was not designed to identify the causes of the infections, so it cannot prove the products were to blame.
Commercial sexual lubricants, which are designed for internal use, were not associated with an increased risk of infection in the study, but they still require further evaluation, according to Brown.
Many personal lubricants, like K-Y jelly, contain glycerin which breaks down to sugars and promotes yeast infections and possibly also bacterial vaginosis, noted Dr. Mary Marnach, a specialist in obstetrics and gynecology at the Mayo Clinic in Rochester, Minnesota.
"For this reason I recommend lubricants without glycerin such as Astroglide Free and those that are silicone based (K-Y Intrigue) over the counter," Marnach said.
Women must navigate an increasing number of products hitting the market every day, Brown noted.
"I have always been fascinated by the vast array of commercially-available over the counter products marketed to women to modify their vaginal environment," she told Reuters Health by email. "In most pharmacies you can find entire aisles dedicated to vaginal douches, suppositories, and gels that are meant to make your vagina smell like a tropical splash or a cookie."
The Food and Drug Administration "strongly urges" cosmetic manufacturers to test their products for safety, but does not require it, Brown said.
SOURCE: http://bit.ly/16q2gDL Obstetrics & Gynecology, online March 6, 2013.