Three common causes of vaginitis present with overlapping symptoms — discharge, irritation, sometimes itching — but each needs completely different treatment. BV responds to antibiotics (metronidazole or clindamycin). Yeast responds to antifungals (fluconazole or topical azoles). Trichomoniasis is an STI that responds to metronidazole or tinidazole plus partner treatment. Get the diagnosis wrong and you waste a course of medication treating the wrong thing. Here's how to tell them apart.
BV has thin grayish discharge with a fishy odor and minimal itching. Yeast has thick white cottage-cheese discharge with intense itching and no strong odor. Trichomoniasis has yellow-green frothy discharge with a strong odor, often itching plus pain with intercourse. Three distinct patterns, three different treatments — and trichomoniasis always needs partner treatment because it's sexually transmitted.
| Feature | Bacterial vaginosis | Yeast infection | Trichomoniasis |
|---|---|---|---|
| Discharge color | Grayish-white | White | Yellow-green |
| Discharge texture | Thin, watery | Thick, cottage-cheese, clumpy | Frothy, often with bubbles |
| Odor | Fishy (worse after sex) | None or mild yeasty | Strong, foul |
| Itching | Minimal | Intense | Often present |
| Pain with sex | Sometimes | Common | Common |
| External redness | Rare | Common, sometimes severe | Possible |
| Transmission | Not classically STI | Not STI | STI — partner treatment required |
| Cause | Bacterial overgrowth (Gardnerella) | Candida fungus | Trichomonas vaginalis (protozoan) |
| Diagnosis | Symptoms, Amsel criteria, sometimes wet mount | Symptoms, wet mount for KOH prep | NAAT (nucleic acid amplification) or wet mount |
| Treatment | Metronidazole or clindamycin | Fluconazole or topical azole | Metronidazole or tinidazole + partner |
| Safe for async telehealth? | Yes (uncomplicated) | Yes (uncomplicated) | No (needs lab + partner workup) |
BV results from an overgrowth of anaerobic bacteria (primarily Gardnerella vaginalis) that displaces normal vaginal lactobacilli, raising the pH. The signature is a thin grayish-white discharge with a fishy odor that worsens after sex or menstruation, usually with little to no itching. CDC first-line treatment is oral metronidazole 500 mg twice daily for 7 days, or vaginal metronidazole gel, or clindamycin.
BV is the most common cause of vaginal discharge in reproductive-age women. Despite not being classified as an STI, sexual activity is one of the strongest risk factors — new partners, multiple partners, and sex without condoms all disrupt vaginal pH. Douching is also a strong driver and should be avoided entirely.
Yeast infections are caused by Candida albicans (or less commonly C. glabrata) overgrowing in the vagina. The signature combination is intense vulvar itching, thick white cottage-cheese-like discharge with no strong odor, and often external redness. CDC and ACOG first-line treatment is oral fluconazole 150 mg single dose, or topical clotrimazole or miconazole for 1, 3, or 7 days.
Yeast infections often follow antibiotic courses (which disrupt normal vaginal flora), pregnancy, uncontrolled diabetes, or immune suppression. Recurrent yeast (four or more episodes in 12 months) is a separate clinical entity that needs culture-based workup and often suppressive therapy.
Trichomoniasis is a sexually transmitted infection caused by the protozoan Trichomonas vaginalis. The signature is a yellow-green, often frothy discharge with a strong odor, plus itching and sometimes pain with urination or intercourse. Diagnosis typically requires NAAT testing or microscopy. CDC treatment is single-dose metronidazole 2 g or tinidazole 2 g, and sexual partners must also be treated to prevent re-infection.
Trichomoniasis is often missed or misdiagnosed because up to 70% of carriers (both male and female) are asymptomatic. When symptoms do appear, they can mimic both yeast and BV, which is why lab confirmation matters. Async telehealth isn't the right setting — partner identification, NAAT testing, and sometimes additional STI screening need to happen in person or through a lab-connected service.
Treating the wrong condition wastes weeks of discomfort. Antifungals don't treat BV. Metronidazole doesn't treat yeast. Topicals don't address trichomoniasis, which also requires partner treatment. Getting the differential wrong isn't usually dangerous, but it delays resolution and can lead to secondary problems (scratching-induced skin breakdown, continued sexual transmission, progression to PID in rare cases with BV or trich).
About 20% of women with vaginitis symptoms have more than one thing going on at once. BV and yeast co-infection is particularly common — they share some risk factors (antibiotic disruption, pregnancy). In mixed cases, a clinician usually treats both sequentially or together, not one and hope the other resolves.
See a clinician in person instead of treating via telehealth if: