Despite widespread medical consensus that douching isn't necessary and can actually harm your lady parts, it is still a common practice. Hazardous ingredients may include unknown fragrance chemicals and the spermicide octoxynol-9. Studies link douche use to bacterial vaginosis, pelvic inflammatory disease, cervical cancer, low-birth weight, preterm birth, HIV transmission, sexually transmitted diseases, ectopic pregnancy, chronic yeast infections, and infertility.