How You Get BV: Triggers & Risk Factors

Bacterial vaginosis (BV) happens when the vagina's normal protective bacteria — mostly Lactobacillus species — get crowded out by an overgrowth of anaerobic bacteria. It isn't a classic sexually transmitted infection, but it's strongly linked to sexual activity. Douching, new or multiple partners, and skipping condoms all raise the odds. You can't catch it from a toilet seat or a pool.

How you get BV: the actual mechanism

BV is an imbalance rather than a bug you catch from one person. A healthy vagina runs slightly acidic, kept that way by Lactobacillus bacteria that produce lactic acid and hydrogen peroxide. That acidity holds anaerobic bacteria in check. When the lactobacilli decline, those anaerobes multiply, the pH climbs, and you get the thin discharge and fishy odor of BV. It's the most common vaginal condition in women ages 15–44 CDC.

Because BV is a shift in the vaginal ecosystem, the things that disrupt that ecosystem are what raise your risk, rather than a single exposure to an infected partner the way gonorrhea works.

Sexual activity and new or multiple partners

BV is not classified as a traditional STI, yet it's clearly associated with sex: women who have never been sexually active are rarely affected. A new partner or multiple partners — including female partners — raises the risk, likely because new sexual contact introduces different bacteria, and semen, which is alkaline, can temporarily nudge the vaginal pH up and disturb the lactobacilli. Sex between women can transmit the bacterial community that tips the balance, and partner concordance is common in female couples.

Douching

Douching is one of the clearest, most preventable triggers. Flushing the vagina with water or scented solutions physically washes out the protective lactobacilli and changes the pH, creating the conditions anaerobes need to take over. The vagina is self-cleaning; douching doesn't make it cleaner, it makes BV more likely. Stopping douching is among the most useful single changes you can make CDC STI guidelines, 2021.

Not using condoms

Skipping condoms is linked to higher BV risk, again because semen exposure can shift the vaginal environment. Using condoms correctly and consistently is associated with a lower rate.

How you do NOT get BV

A lot of worry about BV is misplaced. It does not spread through everyday surfaces or casual contact. You cannot get BV from:

• Toilet seats — the bacteria involved don't survive and transmit this way.
• Bedding, towels, or shared laundry.
• Swimming pools or hot tubs.
• Casual contact like hugging, sharing food, or sitting next to someone.
• Saliva alone or kissing.

BV is about your own vaginal bacterial balance, not a germ lurking on a public surface. If symptoms point to something else entirely, compare your bv symptoms against other causes before you assume the worst.

Who's at higher risk

Anyone with a vagina can develop BV, but some groups carry more of the burden:

• Women who douche regularly.
• Women with a new sex partner or multiple partners, including women who have sex with women.
• Women who don't use condoms.
• Women in their reproductive years — BV is most common between ages 15 and 44.
• Women with a history of BV, because recurrence is common.

BV matters beyond discomfort because it raises the risk of acquiring or transmitting HIV and other STIs. A meta-analysis of more than 30,000 women found BV raised the risk of acquiring HIV by about 60% (RR 1.61), because losing the protective lactobacilli changes the vaginal environment and weakens a natural barrier Atashili et al., AIDS.

BV in pregnancy

BV during pregnancy is associated with preterm delivery (birth before the lungs and other organs are fully ready) and low birth weight, both of which carry health risks for the baby. If you're pregnant and notice unusual discharge or odor, don't self-treat; talk to your prenatal clinician. We cover the specifics of testing and treatment in bv in pregnancy.

Reducing your risk

You can't control every variable in your vaginal ecosystem, but the evidence-backed steps are straightforward:

• Don't douche — let the vagina maintain its own balance.
• Use condoms correctly every time; consistent use is tied to lower BV risk and protects against the sexually transmitted infections too.
• Limit the number of sex partners.
• Skip scented washes, sprays, and deodorizing products in the genital area.
• Get routine STI testing, which catches infections that have no symptoms at all.

BV is common and treatable. Clinics handle it daily, and a diagnosis says nothing about you as a person. The table below sorts the real triggers from the myths.

If you think you've been exposed

Because BV isn't a single-exposure STI, there's no "morning after" exposure window for it the way there is for some infections. But if a new partner or unprotected sex has you worried about STIs in general, check the when to test after exposure guide so you test at the right time and don't get a falsely reassuring early result.

When to see a clinician

See a clinician if you have unusual discharge, a fishy odor (often stronger after sex), itching, or burning — especially if symptoms are new, recurring, or you're pregnant. A clinician confirms BV with a simple exam and vaginal swab rather than guesswork, which matters because yeast infections and trichomoniasis can feel similar but need different treatment. You can learn what that visit involves under bv testing, or simply get tested if you also want a full STI screen.

A course of antibiotics clears most acute episodes, but BV comes back. Standard antibiotics cure 80 to 90% of acute episodes, yet it returns in up to 60% of women within 12 months SASGOG. Three or more episodes a year is considered recurrent BV and often calls for a months-long maintenance regimen rather than repeating a single course.