Vaginal douching is a common practice in the United States and has been linked to increased risk of several sexually transmitted diseases (STDs), including human immunodeficiency virus (HIV) infection. However, because women at high risk for these conditions could be more likely to douche, the association could be real but not cause and effect. Ness and colleagues studied women at high risk for STDs to assess the independent relationship between douching and bacterial vaginosis.

They recruited 1,200 women 13 to 36 years of age who attended one of five clinical sites for gynecologic care. These women were considered at high risk for STDs based on a screening questionnaire developed for a previous study of Chlamydia infection. Specimens were obtained from all patients for Lactobacillus species, Gardnerella vaginalis, Escherichia coli, Candida species, Mycoplasma hominis, Urea-plasma urealyticum, anaerobic gram-negative rods, group B streptococcus, and Enterococcus species. Specimens were also obtained to test for presence of Neisseria gonorrhoeae and Chlamydia trachomatis. Information about douching was included in a detailed interview that covered demographic information, lifestyle issues, and gynecologic, obstetric, and sexual history.

The women were predominantly young (19 to 24 years), unmarried, black, and of low income. Two major brands of douches were used by 87 percent of the women, and the odds ratios relating each brand to bacterial vaginosis or change in vaginal flora were similar for each brand. Douching at least once per month was reported by about 40 percent of participants. The presence of bacterial vaginosis was significantly associated with douching. After adjustment for significant variables, douching at least once per month increased the risk of bacterial vaginosis or intermediate vaginal flora 1.4-fold. The risk increased to 2.1 times in women who douched within one week of the study. No relationship was found between douching and N. gonorrhoeae or C. trachomatis infection.

The authors conclude that douching is significantly related to bacterial vaginosis and changes in the vaginal flora. This finding correlates with data from other studies conducted on different populations of women in several countries. The authors propose that douching disturbs the vaginal protective systems, which are based on hydrogen peroxide and lactobacilli. This disruption of the vaginal microbiology permits overgrowth of the anaerobic and aerobic bacteria responsible for bacterial vaginosis. Because bacterial vaginosis has been linked to the acquisition of HIV, preterm delivery, pelvic inflammatory disease, and other adverse effects, douching could play an important role in multiple health problems among sexually active women.