Discharge that is heavier than usual and has a noticeable odor is most commonly caused by bacterial vaginosis, an overgrowth of certain bacteria in the vagina. On average, the vagina produces less than one teaspoon of discharge daily, so anything significantly beyond that, especially with a strong smell, signals that something has shifted in your vaginal environment. The good news is that the most likely causes are treatable, and understanding what’s behind the change can help you figure out your next step.
What Normal Discharge Looks Like
Healthy vaginal discharge exists on a spectrum. It can be clear, white, or slightly off-white, and it typically has little to no smell. The amount and texture change throughout your menstrual cycle. Around ovulation (roughly days 10 to 14 of your cycle), discharge becomes noticeably wetter, stretchy, and slippery, often compared to raw egg whites. This fertile-window increase lasts about three to four days and is completely normal.
Pregnancy also increases discharge volume. Higher estrogen levels cause the body to produce more fluid, resulting in what’s called leukorrhea: thin, clear or milky white discharge that smells mild or not at all. So if you’re pregnant or near ovulation, a temporary increase in volume alone isn’t necessarily a problem. The red flag is when the smell changes or the discharge takes on an unusual color or texture.
Bacterial Vaginosis: The Most Common Cause
Bacterial vaginosis (BV) is the single most likely explanation for discharge that smells fishy. It happens when the balance of bacteria in the vagina tips away from the protective species (Lactobacillus) and toward other types of bacteria that don’t belong in high numbers. BV discharge is typically thin with a milk-like consistency, and it can look off-white, gray, or greenish. The fishy odor is often stronger after sex or during your period.
A healthy vagina maintains a pH between 3.8 and 4.5. Lactobacillus bacteria are responsible for keeping it that acidic: they feed on sugars produced by vaginal cells and convert them into lactic acid, which disrupts the cell walls of harmful bacteria and makes the environment inhospitable to them. When Lactobacillus gets knocked back, whether by douching, a new sexual partner, or sometimes for no obvious reason, pH rises above 4.5 and BV-associated bacteria flourish. That’s where the smell comes from.
BV is not a sexually transmitted infection, though sexual activity can increase risk. It’s treated with antibiotics, either taken orally or applied as a vaginal gel. Many people notice improvement within a few days, but recurrence is common, with some estimates suggesting about half of those treated experience BV again within 12 months.
Trichomoniasis: An STI That Mimics BV
Trichomoniasis (trich) is a sexually transmitted infection caused by a parasite, and it produces symptoms that overlap heavily with BV. Discharge can be clear, white, yellowish, or greenish, and it often has a fishy smell. One feature that sometimes helps distinguish trich from BV is that trich discharge can appear frothy or bubbly, whereas BV discharge tends to be thin and smooth.
Other symptoms of trich include itching, burning during urination, and redness or soreness around the genitals. Many people with trich have no symptoms at all, so a partner can pass it along without knowing. It’s diagnosed through a lab test and treated with a single course of oral antibiotics. Both you and your sexual partner need treatment at the same time to prevent reinfection.
Other Infections That Change Discharge
Yeast Infections
A yeast infection produces thick, white, cottage cheese-like discharge. Unlike BV and trich, yeast infections usually do not cause a strong or fishy smell. The hallmark symptoms are intense itching, burning, and irritation rather than odor. If your main concern is smell rather than itch, a yeast infection is less likely to be the cause.
Chlamydia and Gonorrhea
Both chlamydia and gonorrhea can cause increased vaginal discharge, but they don’t always produce a distinctive odor. Gonorrhea discharge tends to be thick, cloudy, or even bloody. Chlamydia discharge is often mild enough that many people don’t notice it at all. Both infections can be present with no symptoms, which is why STI screening matters if you’ve had unprotected sex or a new partner. Left untreated, both can lead to pelvic inflammatory disease and affect fertility.
What Makes Odor and Discharge Worse
Douching is one of the most common habits that backfires. It temporarily washes out protective Lactobacillus bacteria, and the vinegar or fragrance solutions used in douches cannot replicate the antimicrobial effect of the lactic acid those bacteria produce. Research from Fred Hutchinson Cancer Center found that acetic acid (vinegar) simply doesn’t disrupt harmful bacteria the way lactic acid does. The result: douching often causes the exact problem it’s trying to fix.
Other factors that can shift your vaginal balance include scented soaps or body washes applied directly inside or around the vagina, tight non-breathable underwear, leaving a tampon in too long, and antibiotics taken for unrelated conditions (since they can kill off Lactobacillus along with the targeted infection). Semen also temporarily raises vaginal pH, which is why some people notice a stronger smell after unprotected sex.
How It Gets Diagnosed
A healthcare provider can usually identify the cause of smelly discharge through a pelvic exam and a sample of the discharge. For BV, doctors look at the discharge under a microscope for cells coated in bacteria (called clue cells), check the vaginal pH, and assess the odor. They may also send a swab for STI testing, particularly for trich, chlamydia, and gonorrhea, since these infections can coexist.
Home pH test strips are available over the counter and can give you a rough idea of whether your pH is elevated, but they can’t tell you which specific infection you have. A pH above 4.5 points toward BV or trich rather than a yeast infection, but confirming the cause requires a lab result. If you’ve had smelly discharge for more than a few days, or if it’s accompanied by pelvic pain, fever, or bleeding between periods, getting tested is the clearest path to the right treatment.
Keeping Your Vaginal Flora Healthy
The vagina is largely self-cleaning, so the simplest protective strategy is to stop interfering with it. Skip douches entirely. Wash the external vulva with warm water or a mild, unscented soap, and leave the inside alone. Wear cotton underwear or at least underwear with a cotton crotch panel, and change out of wet swimsuits or sweaty workout clothes promptly.
Some people find that probiotic supplements containing Lactobacillus strains help reduce BV recurrence, though the evidence is mixed. What’s well established is that the more you disrupt the existing Lactobacillus population, whether through douching, fragranced products, or frequent antibiotic use, the harder it is for those bacteria to maintain the acidic environment that keeps infections at bay.