BV, a yeast infection, and trichomoniasis all cause discharge, itching, and irritation, but they differ in cause and cure. BV and trich produce a thin discharge with a fishy odor; yeast brings thick, white, odorless discharge with intense itching. BV is a bacterial imbalance, yeast is fungal, and trich is a sexually transmitted parasite. Only a test reliably tells them apart.
most common curable STI; metronidazole
not an STI; recurs in up to 60%
not an STI; antifungal cure
| Item | Value |
|---|---|
| Trichomoniasis | curable — most common curable STI; metronidazole |
| Bacterial vaginosis (BV) | curable — not an STI; recurs in up to 60% |
| Vaginal yeast infection (candidiasis) | curable — not an STI; antifungal cure |
What each one is
Trichomoniasis
Trichomoniasis is caused by a single-celled parasite, Trichomonas vaginalis, and it's the most common curable non-viral STI in the US, with an estimated 2.6 million infections and women accounting for over 80% of cases Sex Transm Dis, 2018. Unlike BV and yeast, trich is spread through sex, so a diagnosis means partners need treatment too. About 70% of infected people have no symptoms CDC, so it persists and passes between partners unnoticed.
Bacterial vaginosis (BV)
BV isn't a single germ. It's an imbalance: the protective Lactobacillus bacteria that normally dominate the vagina get crowded out by anaerobic bacteria, shifting the whole environment. It's the most common vaginal condition in women ages 15–44 CDC. BV isn't classed as an STI, though sexual activity can disturb the bacterial balance that triggers it. Many people with BV notice nothing; for more, see our guide to bv symptoms.
Vaginal yeast infection (candidiasis)
A yeast infection is fungal, almost always caused by Candida albicans overgrowing in the vagina. It's one of the most common fungal infections and is not usually acquired through sex CDC, so it isn't an STI and partners generally don't need treatment. Antibiotics, pregnancy, diabetes, and a weakened immune system can all tip the balance toward overgrowth. A deeper rundown lives in our page on yeast infection symptoms.
Symptoms compared
The discharge itself is your single most useful clue, but it's far from foolproof:
- Trichomoniasis: itching, burning, redness or soreness of the genitals; discomfort urinating; and a clear, white, yellowish or greenish discharge that may carry a fishy smell. Men, when they have symptoms at all, get itching inside the penis, burning after urinating or ejaculating, or discharge, but they are commonly asymptomatic.
- BV: a thin white or gray discharge with a strong fish-like odor that's often worse after sex, sometimes with itching, burning, or burning on urination. Many people have no symptoms.
- Yeast: vaginal itching or soreness, a thick, white (cottage-cheese-like) discharge with little or no odor, pain during sex, and discomfort urinating. Severe cases bring redness, swelling, and small cracks in the vaginal wall.
How to tell them apart
A few features do the discriminating work. A fishy smell points toward BV or trich, while yeast is essentially odorless. Texture splits the other two: yeast discharge is thick and white, BV and trich discharge tends to be thin. Itching tends to be worst with yeast. Vaginal pH is the clinician's tiebreaker, normal (under 4.5) with yeast but elevated (over 4.5) with BV and frequently with trich.
These patterns overlap enough that you usually can't tell them apart by feel. Greenish discharge leans trich, cottage-cheese leans yeast, fishy-after-sex leans BV, but plenty of cases break the rules, and you can have more than one at once. A test settles it and spares you from treating the wrong thing. Reaching for an over-the-counter yeast cream when the real problem is BV or trich is one of the most common mistakes, and it delays the cure you need.
Side-by-side comparison
| Feature | Trichomoniasis | BV | Yeast infection |
|---|---|---|---|
| Cause | Parasite (T. vaginalis) | Bacterial imbalance | Fungus (Candida) |
| Is it an STI? | Yes | No (sex can trigger it) | No |
| Discharge | Clear/yellow/green, thin, sometimes frothy | Thin, white or gray | Thick, white, cottage-cheese-like |
| Odor | Fishy | Strong fishy, worse after sex | Little or none |
| Itching | Common | Sometimes | Often intense |
| Vaginal pH | Often elevated (>4.5) | Elevated (>4.5) | Normal (<4.5) |
| Partner treatment | Yes | No | No |
Testing
Each one has its own preferred test, so a clinician's confirmation beats guesswork:
- Trich: a nucleic acid amplification test (NAAT) is preferred. Assays like the Aptima T. vaginalis test run roughly 95–100% sensitive CDC STI Tx Guidelines, 2021, using a vaginal swab or a female urine sample. More detail on the process is in our guide to trichomoniasis testing & diagnosis.
- BV: diagnosed by Amsel criteria (three or more of: thin discharge, clue cells under the microscope, vaginal pH over 4.5, and a positive whiff test), by a Nugent score on a Gram stain (the reference standard) CDC, or by an FDA-cleared molecular test.
- Yeast: confirmed by looking at discharge under a microscope (a wet prep with saline or KOH showing budding yeast, hyphae, or pseudohyphae) and/or a fungal culture; a normal vaginal pH is a supporting clue CDC.
In practice, testing is quick: a urine sample, a self-collected swab, or a brief exam depending on what's suspected. It's free or low-cost at health departments, Planned Parenthood, and Title X clinics. If a parasite or other STI is on the table, you can get tested for trich alongside the rest, and if you're testing after a specific encounter, check when to test after exposure so you don't test too early.
Treatment compared
Because the causes differ, the cures don't overlap. Antibiotics won't touch yeast, and antifungals won't touch BV or trich.
- Trich: for women, the recommended regimen is metronidazole 500 mg orally twice daily for 7 days; men get metronidazole 2 g orally as a single dose, with tinidazole 2 g single dose as an alternative for either. The 2021 guidelines moved women off the old single 2 g dose because the multi-day course works better. In a randomized trial, about 19% of women given the single dose were still infected at follow-up versus 11% on the 7-day course Muzny et al., Sex Transm Dis. Partners need treatment, and you should avoid sex until everyone is cured.
- BV: recommended options are metronidazole 500 mg orally twice daily for 7 days, metronidazole 0.75% gel intravaginally once daily for 5 days, or clindamycin 2% cream intravaginally at bedtime for 7 days.
- Yeast: for uncomplicated cases, intravaginal azoles (such as clotrimazole 1% cream for 7–14 days or miconazole 2% cream for 7 days, many over-the-counter) or a single oral dose of fluconazole 150 mg.
Both BV and yeast tend to recur. Standard antibiotics clear 80 to 90% of acute BV episodes, but it returns in up to 60% of women within a year SASGOG, so recurrent BV (three or more episodes annually) usually calls for a months-long maintenance regimen rather than another single course. Recurrent yeast (four or more symptomatic episodes in a year) is treated with an induction course followed by weekly fluconazole for months RVVC review; stubborn cases can involve a non-albicans Candida that resists the usual fluconazole.
Can you have more than one at once?
Yes. Co-infections are common, which is another reason self-diagnosis fails. Trich frequently travels with BV, and the symptoms of all three can blur together. BV also matters beyond discomfort: a meta-analysis of more than 30,000 women found BV raised the risk of acquiring HIV by about 60% Atashili et al., AIDS, because losing protective lactobacilli changes the vaginal environment. If one infection is confirmed but treatment doesn't fully clear your symptoms, a second cause is often the explanation.
When to see a clinician
See a clinician if it's your first episode of these symptoms, if symptoms are severe, if they don't improve after treatment, if they keep coming back, or if you're pregnant. The symptoms resemble one another closely, and trich is sexually transmitted while yeast and BV are not, so a test is the only way to be sure you're treating the right thing and protecting any partners who also need care.