A vaginal odor that smells like feces usually has one of a few explanations, ranging from simple hygiene factors to a medical condition that needs treatment. The vagina and anus sit very close together, which makes fecal bacteria transfer surprisingly common. But a persistent, strong fecal smell, especially one that doesn’t go away with normal washing, points to something that deserves attention.
Fecal Bacteria Transfer From Normal Anatomy
The most straightforward explanation is also the most common. The vagina sits only a short distance from the anus, and bacteria from the rectum can easily migrate forward. This can happen during wiping (back to front instead of front to back), during sex, or simply from sweat and moisture throughout the day. When fecal bacteria colonize the vaginal area, they can produce an odor that smells distinctly like stool.
This type of odor is typically mild and temporary. It resolves with proper hygiene: wiping front to back, washing the external vulva with warm water, and wearing breathable cotton underwear. Avoid douching or using scented products inside the vagina, as these disrupt the natural bacterial balance and can make odor problems worse. A healthy vagina maintains a slightly acidic environment (pH between 3.8 and 4.5) that keeps harmful bacteria in check. Anything that shifts that balance gives odor-causing bacteria room to grow.
A Forgotten Tampon or Retained Object
A tampon left in too long is one of the most common causes of a sudden, overwhelming vaginal smell that people describe as rotten or fecal. It happens more often than you’d think: a tampon gets pushed to the back of the vaginal canal during sex, or you insert a new one and forget the old one is still there.
As the retained object breaks down and bacteria multiply around it, the smell becomes extremely strong and foul. You may also notice unusual discharge. Tampons should be changed every 4 to 6 hours, and manufacturers recommend never leaving one in longer than 8 hours. If left for days or weeks, a retained tampon can cause infection and, in very rare cases, toxic shock syndrome. If you suspect a forgotten tampon, you can try to remove it yourself by reaching in with clean fingers. If you can’t find or reach it, a healthcare provider can remove it quickly in an office visit.
Bacterial Vaginosis and Infection
Bacterial vaginosis (BV) is the most common vaginal infection, caused by an overgrowth of certain bacteria. BV is classically described as producing a “fishy” smell, especially after sex. While fishy and fecal aren’t the same, strong odors can be hard to categorize precisely, and some people experience BV odor as generally foul rather than specifically fishy.
BV develops when the normal balance of vaginal bacteria shifts, allowing less desirable species to take over. It often comes with thin, grayish-white discharge. To diagnose it, a provider takes a sample of vaginal discharge and runs tests, some of which give results the same day. If you’re planning to get tested, avoid vaginal medications for at least 3 days beforehand, and skip douching, sex, and spermicides before your appointment, as these can interfere with accurate results.
Rectovaginal Fistula: When Stool Leaks Through
If the smell is unmistakably fecal and you notice gas or actual stool coming from your vagina, the cause may be a rectovaginal fistula. This is an abnormal opening between the rectum and the vagina that allows bowel contents to pass through. The most obvious symptom is passing gas or stool from the vagina. Some fistulas are small enough that you only notice a foul-smelling discharge, while larger ones cause significant leakage.
The most common cause is injury during childbirth, particularly tears in the perineum (the tissue between the vagina and anus) that extend deep enough to involve the bowel. The second most common cause is inflammatory bowel disease, especially Crohn’s disease. Other causes include pelvic surgery complications, radiation treatment for cancer, and diverticulitis (infection of small pouches in the digestive tract).
Rectovaginal fistulas are uncommon but not as rare as you might assume. Among women who’ve had rectal cancer surgery, for instance, about 3.2% develop one. Because the symptoms are so disruptive, surgical repair is almost always recommended. Before surgery, the tissues typically need 6 to 12 weeks to heal and settle down from any active inflammation. After repair, managing bowel habits becomes important: the goal is soft, formed stools, achieved through diet, plenty of fluids, and stool softeners. Constipation or diarrhea can both compromise the repair.
Metabolic Conditions That Affect Body Odor
In rare cases, a fecal or intensely fishy smell from the vagina is caused by a metabolic disorder rather than a local infection. One example is trimethylaminuria, a condition where the body can’t properly break down a compound called trimethylamine. Normally, your liver converts this substance into an odorless form that leaves in your urine. People with this condition excrete the smelly, unprocessed version through urine, sweat, breath, and vaginal secretions.
Research has found that women with fishy-smelling vaginal discharge sometimes have a reduced ability to process this compound compared to healthy controls. The condition is genetic and lifelong, though dietary changes (reducing certain foods like fish, eggs, and legumes that are high in the precursor compounds) can help manage the smell. If you’ve had persistent vaginal odor that doesn’t respond to infection treatment, this is worth discussing with a provider.
How to Narrow Down the Cause
Start by considering when the smell started and what else is happening. A sudden onset after your period or sex suggests a retained tampon or BV. An odor that appeared after childbirth, pelvic surgery, or alongside symptoms of Crohn’s disease raises the possibility of a fistula. A lifelong pattern of strong body odor affecting multiple areas (not just the vagina) points toward a metabolic cause.
Pay attention to accompanying symptoms. Discharge color and consistency matter: thin and grayish suggests BV, while brownish or blood-tinged discharge with a terrible smell suggests a retained object. Passing gas from the vagina is a hallmark of a fistula. Pain, fever, or feeling generally unwell alongside the odor signals an active infection that needs prompt care.
A provider can usually identify the cause with a physical exam and discharge sample. For suspected fistulas, imaging studies may be needed. The important thing is that every cause of fecal vaginal odor is treatable, whether that means a course of antibiotics, removing a forgotten tampon, or surgical repair of a fistula.