Yeast infections and bacterial vaginosis (BV) are the two most common causes of vaginal discomfort, and they’re often confused because they share some overlapping symptoms. But they have different causes, different warning signs, and require completely different treatments. Using the wrong one can make things worse, so telling them apart matters.
What Causes Each Condition
BV and yeast infections both involve disruptions to the vaginal microbiome, but the disruptions go in opposite directions. A healthy vagina is dominated by lactobacilli, bacteria that produce hydrogen peroxide and keep the environment slightly acidic. This acidity holds other organisms in check.
In BV, the lactobacilli population drops and anaerobic bacteria rush in to fill the gap. The process likely starts with a species called Gardnerella, which forms a biofilm on the vaginal walls and creates a hospitable environment for other opportunistic bacteria. The result is a dramatic shift in the entire microbial community, not just a single invader.
A yeast infection works differently. The fungus Candida albicans is responsible for the vast majority of cases. Candida naturally lives in the vagina in small numbers, kept in check by lactobacilli and the immune system. When something tips that balance (antibiotics wiping out protective bacteria, a spike in blood sugar from poorly controlled diabetes, immunosuppression, or hormonal shifts), Candida overgrows. It’s a fungal overgrowth, not a bacterial one.
How the Symptoms Differ
The fastest way to tell these two apart at home is by paying attention to discharge and odor.
- BV discharge is typically thin, grayish, and sometimes foamy. It has a noticeable fishy smell that can get stronger after sex. That odor comes from chemical compounds called amines that anaerobic bacteria produce.
- Yeast infection discharge is thick, white, and often described as cottage cheese-like. It has no unusual odor.
Itching is another key divider. Yeast infections almost always cause significant itching, burning, and irritation of the vulva and vaginal opening. You may also notice redness, swelling, or a white coating on the skin. BV, on the other hand, often causes little to no itching. Many people with BV notice the smell and discharge but don’t have much external irritation. In fact, about half of people with BV have no noticeable symptoms at all.
Vaginal pH as a Clue
The vaginal pH of someone with BV is consistently elevated above 4.5, because the loss of acid-producing lactobacilli allows the environment to become less acidic. This is one of the four clinical criteria doctors use to diagnose BV.
With a yeast infection, vaginal pH stays in the normal range, right around 4.0. The lactobacilli are still present and doing their job. The problem is fungal overgrowth happening alongside an otherwise intact bacterial community. Over-the-counter pH test strips can pick up this difference, which is why some home testing kits use pH as a screening tool. A normal pH with itching and thick white discharge points toward yeast. An elevated pH with thin, odorous discharge points toward BV.
Risk Factors for Each
Neither BV nor yeast infections are considered sexually transmitted infections, but sexual activity does play a role in BV risk. New sexual partners, multiple partners, and douching all increase the likelihood of developing BV by disrupting the vaginal bacterial balance. BV is more common in people who have sex with women, likely because vaginal bacteria transfer between partners.
Yeast infections are driven more by internal factors. The classic triggers include recent antibiotic use (which kills off protective bacteria and lets Candida flourish), uncontrolled diabetes, pregnancy, hormonal contraceptives, and anything that suppresses the immune system. People living with HIV have higher rates of vaginal Candida colonization, and the risk rises as immune function declines. You can develop a yeast infection without any sexual contact at all.
Why the Right Treatment Matters
This is where the distinction becomes most practical: BV requires antibiotics, while yeast infections require antifungals. Using an antifungal cream for BV won’t clear the bacterial overgrowth. Using antibiotics for a yeast infection can actually make it worse by killing off more lactobacilli and giving Candida even more room to grow.
Yeast infections are typically treated with an antifungal cream applied inside the vagina or a single oral dose of fluconazole. Most uncomplicated cases clear within a few days. For people who get recurrent yeast infections (four or more per year), the treatment approach changes. About 10 to 20 percent of recurrent cases involve non-albicans Candida species that don’t respond as well to standard antifungals, so your provider may need to try alternative options.
BV treatment involves a course of oral or vaginal antibiotics, typically taken for five to seven days. The condition has a frustratingly high recurrence rate. Many people find that BV returns within a few months of treatment, sometimes repeatedly. Researchers believe this happens because the Gardnerella biofilm persists on the vaginal wall even after antibiotics reduce the bacterial count, allowing the community to rebuild.
What Happens if You Don’t Treat It
An untreated yeast infection is uncomfortable but rarely dangerous for people with healthy immune systems. It won’t resolve on its own in most cases, and symptoms tend to worsen, but serious complications are uncommon.
Untreated BV carries more significant risks. It increases susceptibility to sexually transmitted infections, including HIV, chlamydia, and gonorrhea. Those STIs can in turn lead to pelvic inflammatory disease, which can cause lasting damage to the reproductive tract and make it harder to get pregnant. During pregnancy, BV raises the risk of preterm delivery and low birth weight (babies born under 5.5 pounds). For these reasons, BV during pregnancy is treated even when symptoms are mild or absent.
Can You Have Both at Once?
Yes, and it’s not uncommon. The antibiotic treatment for BV can itself trigger a yeast infection by depleting lactobacilli, so some people finish their BV medication only to develop yeast symptoms a few days later. If you’re experiencing a mix of symptoms that doesn’t fit neatly into one category (fishy odor plus significant itching, for example), it’s worth getting tested rather than guessing. A provider can check your vaginal pH, examine the discharge under a microscope, and identify exactly what’s going on so you get the right treatment the first time.