Vaginal infections: thrush and bacterial vaginosis

Vaginal discharge and itching have two common causes with different treatments, and getting the diagnosis right is most of the work.

Vulvovaginal candidiasis (thrush). A topical azole (clotrimazole, miconazole) or oral fluconazole cures most cases, and the evidence is strong. For recurrent thrush, boric acid vaginal capsules have randomised trial evidence and are used medically for azole-resistant Candida glabrata. Boric acid is toxic if swallowed, and it must not be used orally or in pregnancy — deaths have occurred from ingestion, and it is a documented hazard to children and pets. It is a genuine treatment with a genuine hazard.

Bacterial vaginosis. A shift in the vaginal flora with a fishy-smelling discharge. The treatments are metronidazole or clindamycin, which are effective, and recurrence is common. Boric acid has been used as an adjunct for recurrent BV. Probiotics have been tried with inconsistent results. The important point: BV is associated with preterm birth and with an increased risk of acquiring STIs, so it is not a cosmetic problem to self-treat.

What does not work. Yogurt inserted vaginally (trials show no benefit and it introduces bacteria); garlic vaginally (it burns and causes chemical injury — a documented harm); tea tree oil vaginally (burns the mucosa); and douching, which disrupts the flora and increases the risk of BV and pelvic inflammatory disease.

The rule that matters. The two conditions look different — thrush: thick white discharge, itching, no smell; BV: thin grey discharge with a fishy smell, no itching — but they overlap, and a first episode, or a failure to improve, or recurrent symptoms need examination. A discharge that is new, or with pelvic pain, or with fever, or in a woman with a new partner, needs assessment for sexually transmitted infection.

What genuinely reduces recurrence. Avoiding douching and scented products; not using strong soaps on the vulva; cotton underwear and avoiding tight synthetic clothing; treating diabetes well if present; and for recurrent BV, discussing longer or suppressive treatment with a clinician.