Many health care professionals state that douching is dangerous, as it interferes with both the vagina's normal self-cleaning and with the natural bacterial culture of the vagina, and it might spread or introduce infections. For example, the U.S. Department of Health and Human Services strongly discourages douching, warning that it can lead to irritation, bacterial vaginosis, and pelvic inflammatory disease (PID). Frequent douching with water may result in an imbalance of the pH of the vagina, and thus may put women at risk for possible vaginal infections, especially yeast infections.