Vaginal odor usually comes from shifts in the balance of bacteria that naturally live in the vagina. A mild, slightly musky scent is normal and changes throughout your menstrual cycle, but a strong or fishy smell typically points to an overgrowth of certain bacteria, an infection, or an outside factor like sweat, hormonal changes, or a retained object. Most causes are treatable and common.
Bacterial Vaginosis: The Most Common Cause
Bacterial vaginosis (BV) is responsible for the majority of noticeable vaginal odor. It happens when the protective bacteria in the vagina (mostly Lactobacillus species) are outnumbered by other organisms. Those organisms produce volatile chemicals, specifically dimethylamine and trimethylamine, that create a distinct fishy smell. In more advanced cases, the vaginal fluid also contains high levels of compounds called putrescine and cadaverine, the same chemicals produced during tissue decomposition.
The smell from BV often becomes stronger after sex or during your period. That’s because semen and menstrual blood are alkaline, and alkaline conditions cause the odor-producing amines to become airborne more easily. Along with the smell, BV typically causes a thin, grayish-white discharge. Some people have no other symptoms at all.
BV is treated with a course of oral or vaginal antibiotics, usually over five to seven days. It has a frustrating tendency to come back. Roughly half of people treated for BV experience a recurrence within a year, which is why understanding the other factors on this list matters for long-term management.
Trichomoniasis and Other Infections
Trichomoniasis is a sexually transmitted infection caused by a parasite. It produces a fishy odor similar to BV but is usually accompanied by more noticeable discharge that can be clear, white, yellowish, or greenish with a thin or frothy texture. Itching, burning during urination, and vulvar irritation are also common. Many people with trichomoniasis have no symptoms, so a persistent unusual odor after BV has been ruled out is worth testing for.
Yeast infections, by contrast, rarely cause a strong odor. They’re more associated with thick, white discharge and intense itching. If smell is your primary concern, yeast is less likely to be the culprit.
A Forgotten Tampon or Other Retained Object
A tampon left in too long is one of the most dramatic causes of vaginal odor. The smell is often described as extremely foul or rotten, and it develops because bacteria break down the trapped material in a warm, enclosed space. Tampons should be changed every four to six hours, and manufacturers advise against leaving one in for more than eight hours.
Beyond odor, a retained tampon raises the risk of infection and, in rare cases, toxic shock syndrome. If you notice a sudden, overwhelming smell and can’t account for it, checking for a forgotten tampon (or having a clinician check) is a reasonable first step. The odor resolves quickly once the object is removed.
Sweat and External Odor
Not all genital odor actually originates inside the vagina. The vulva and groin are dense with apocrine sweat glands, the same type found in your armpits. These glands release thick, oily sweat that has little smell on its own, but when skin bacteria break it down, it produces a strong, musky odor. This is the same process behind body odor elsewhere on your body, just in a more enclosed area with less airflow.
Tight clothing, synthetic underwear, and panty liners all reduce breathability and trap moisture, creating ideal conditions for bacterial overgrowth on the skin’s surface. Cotton underwear wicks moisture and allows airflow. Cleveland Clinic dermatologists specifically recommend 100% cotton over synthetic fabrics with a cotton crotch panel, noting that the small panel doesn’t fully protect against moisture buildup. If you’re prone to recurrent vulvar irritation or odor, looser-fitting, fully cotton underwear makes a meaningful difference.
Hormonal Changes
Estrogen plays a central role in maintaining the vaginal environment. It keeps the vaginal walls thick and well-supplied with glycogen (a sugar that feeds protective Lactobacillus bacteria). When estrogen drops, as it does during menopause, breastfeeding, or certain points in the menstrual cycle, the vaginal walls thin, moisture decreases, and pH rises. A higher pH means less acidic conditions, which favors odor-producing bacteria over the protective ones.
After menopause, this shift becomes more permanent. The vagina’s pH can climb significantly, and the resulting change in bacterial balance often produces a noticeable change in scent. This is a normal part of aging, not a sign of poor hygiene. Vaginal estrogen therapy, prescribed by a clinician, can help restore the prior balance for people who find the changes bothersome.
Douching Makes Things Worse
Douching is one of the most counterproductive things you can do for vaginal odor. The surfactant detergents in douching products disrupt cell membranes and have antimicrobial activity, but they don’t discriminate between harmful and protective bacteria. Research published in the American Journal of Epidemiology found that douching washes away the antibacterial agents naturally present in vaginal fluid and irritates mucosal surfaces, increasing susceptibility to infection. When women in the study douched with antiseptic solutions, the resulting disruption of Lactobacillus allowed faster-growing pathogenic organisms to take over.
In short, douching to treat odor often causes the exact conditions that produce odor. The vagina is self-cleaning. Warm water on the external vulva is sufficient for hygiene.
Diet and Metabolic Conditions
What you eat can influence how your body smells, including genital odor. Strongly flavored foods like garlic, onions, and certain spices can temporarily alter the scent of sweat and vaginal secretions. These changes are short-lived and harmless.
A rarer cause is trimethylaminuria, a genetic metabolic disorder in which the body cannot break down a compound called trimethylamine. Normally, a liver enzyme converts this strong-smelling chemical (produced by gut bacteria during digestion of eggs, legumes, liver, and certain fish) into an odorless form. When the enzyme is missing or reduced, trimethylamine builds up and is released through sweat, urine, and breath, producing a persistent fishy smell that can be mistaken for BV. The key difference is that trimethylaminuria doesn’t respond to antibiotics and affects multiple body secretions, not just vaginal discharge. It’s diagnosed through a urine test.
When Odor Signals Something Treatable
A mild, fluctuating scent is part of normal vaginal physiology. But certain patterns point to specific, treatable causes worth addressing:
- Fishy smell that worsens after sex or during your period: most commonly BV
- Fishy smell with green or frothy discharge: trichomoniasis
- Sudden, overwhelming foul odor: retained tampon or foreign object
- Musky odor concentrated on the skin: apocrine sweat, often improved with breathable fabrics
- Gradual change in scent after age 50: hormonal shifts affecting vaginal pH
- Persistent fishy smell affecting sweat, urine, and breath: possible trimethylaminuria
If you’ve noticed a change that persists for more than a few days, doesn’t improve with basic hygiene adjustments, or comes with discharge, itching, or burning, testing for BV and trichomoniasis is straightforward and gives you a clear answer.