The drugstore aisle is where the mix-up starts

Both conditions make people buy a box before anyone looks at a sample under a microscope. The CDC's vulvovaginal candidiasis chapter is blunt about that habit. Even people who have had a clinician-diagnosed yeast infection before are not necessarily better at diagnosing the next one. Unnecessary over-the-counter antifungal use is common and can delay treatment of other causes of vulvovaginitis. If symptoms are still there after an over-the-counter product, or if they come back less than two months after yeast treatment, you should be examined and tested.

Bacterial vaginosis and yeast are different problems that share a neighborhood. One is a shift toward anaerobic bacteria. The other is an overgrowth of yeast, usually Candida albicans. Antifungal medicine does not treat BV. Metronidazole does not treat yeast. Using the wrong one wastes days and can let the real problem continue.

Yeast, in the CDC's terms

Vulvovaginal candidiasis is usually caused by Candida albicans and occasionally by other Candida species. The CDC estimates that 75% of women will have at least one episode, and 40% to 45% will have two or more. About 10% to 20% of women will have complicated disease. Complicated means recurrent, severe, caused by a non-albicans yeast, or occurring in someone with diabetes, immune suppression, or medicines such as corticosteroids.

Typical symptoms are itching, vaginal soreness, pain with sex, burning on the outside when urine hits the skin, and a change in discharge. None of those symptoms is specific. Signs clinicians look for include vulvar swelling, small cracks in the skin, scratch marks, and thick, curdy discharge. Vaginal pH stays under 4.5, which is one of the lab clues that separates yeast from BV.

About 10% to 20% of women carry Candida or other yeasts in the vagina with no symptoms. Finding yeast on a culture when nothing hurts or itches is not a reason to treat. Diagnosis, when symptoms are present, uses a wet mount (saline and 10% potassium hydroxide) looking for budding yeast, hyphae, or pseudohyphae, or a culture or other test. If the microscope is negative and symptoms continue, culture is worth doing. Most yeast PCR tests are not FDA-cleared.

Uncomplicated disease is sporadic, mild to moderate, likely C. albicans, and in someone who is not immunocompromised. Short courses of topical azoles work for that group. The CDC says azole treatment relieves symptoms and produces negative cultures in 80% to 90% of people who finish therapy. Over-the-counter options in the guideline include clotrimazole creams, several miconazole creams and suppositories (including a single 1,200 mg suppository), and a single application of tioconazole 6.5% ointment. Prescription options include terconazole and a single 150 mg dose of oral fluconazole. The creams and suppositories are oil-based and might weaken latex condoms and diaphragms.

Pregnancy changes the choice. Only topical azoles, used for 7 days, are recommended. The CDC says epidemiologic studies indicate a single 150 mg dose of fluconazole might be associated with spontaneous abortion and with congenital anomalies, so it should not be used in pregnancy.

Recurrent yeast means three or more symptomatic episodes in less than a year. It affects fewer than 5% of women. Most of those people have no obvious underlying disease, though frequent antibiotics and diabetes are among the secondary causes. Non-albicans species, including Candida glabrata, show up in 10% to 20% of recurrent cases and respond less well to azoles. A longer first treatment is used to try to clear the yeast, then maintenance, often oral fluconazole once a week for 6 months. Maintenance controls symptoms. It rarely cures the tendency long term. For non-albicans yeast that recurs, the CDC says 600 mg of boric acid in a gelatin capsule, vaginally, once a day for 3 weeks, has clinical and mycologic eradication rates around 70%. That capsule is a vaginal medicine under a clinician's direction. It is toxic if swallowed. No substantial evidence supports probiotics or homeopathic products for treating yeast infections.

Sex partners are not routinely treated. Uncomplicated yeast is not usually acquired through intercourse. A male partner with balanitis, redness and itching on the glans, can use a topical antifungal for his own symptoms.

Bacterial vaginosis, side by side

BV is the most common vaginal condition in women ages 15 to 44, according to CDC patient information, and the STI guidelines call it the most common cause of vaginal discharge worldwide. Lactobacillus gives way to anaerobic bacteria such as Gardnerella vaginalis. The discharge people notice is thin and homogeneous, white or gray, not thick and curdy. The odor is fish-like and often stronger after sex. Itching can happen, but it is not the dominant feature the way it is with yeast. pH is greater than 4.5. Clue cells and a positive whiff test are part of Amsel's criteria, which are spelled out in Bacterial Vaginosis: Causes, Symptoms, and Treatments.

Many people with BV have no symptoms. A Pap test does not diagnose it. Culture of Gardnerella alone is not specific enough to use.

Recommended treatment is metronidazole by mouth or as a gel, or clindamycin cream, in the doses in the CDC guideline. Tinidazole, secnidazole, and oral clindamycin are alternatives. Antifungal cream is not on that list. As with yeast creams, clindamycin cream can weaken latex condoms for several days.

BV is tied to sexual activity in ways yeast usually is not. New or multiple partners, not using condoms, and douching raise risk. It rarely affects people who have never had sex. It is still not classified by the CDC patient page as something you get from a toilet seat, and male partners are not routinely treated. It can pass between female partners. In pregnancy, symptomatic BV is tied to preterm birth and low birth weight, so it should be treated. Yeast in pregnancy is treated with topical azoles, as above. The medicines are not interchangeable just because both say "vaginitis" on a chart.

A practical comparison

Hold the two patterns next to each other, then throw the comparison out if a test disagrees with it.

  • Itch. Often the main complaint in yeast. In BV it may be mild or absent.
  • Discharge. Yeast is linked with thick, curdy discharge. BV is linked with thin, milk-like, white or gray discharge.
  • Smell. Yeast usually has little odor. BV often smells fish-like, worse after sex.
  • pH, if someone measures it. Under 4.5 fits yeast. Over 4.5 is one of the Amsel findings in BV.
  • Medicine that matches CDC guidance. Azole antifungals for yeast. Metronidazole, clindamycin, or the other listed antibiotics for BV.

That list is a conversation starter. It is not a diagnosis. Trichomoniasis can look like either one: discharge, irritation, and sometimes odor. The CDC wants clinicians to look for it, and for other STIs, rather than stopping at the first familiar label. Some clinic panels test for yeast, BV organisms, and trichomonas on one swab. Overlapping positive results happen. A clinician treats what is actually there.

What to do with the box you already bought

If you used an antifungal and you are well, you may have treated uncomplicated yeast. If you are not well, stop guessing. See someone who can check pH, do a microscope exam or a proper test, and test for STIs when the history suggests them. Go sooner if you are pregnant, if you have fever or pelvic pain, if this is the third episode this year, or if you have diabetes that is not well controlled. Poorly controlled diabetes is one of the host factors the CDC ties to complicated yeast and to a weaker response to short courses.

The useful question before the visit is whether the last treatment was an antifungal or an antibiotic, and whether the itch or the smell was what bothered you more.

Sources

Education only. Pregnancy, recurrent symptoms, and pelvic pain need in-person testing. Do not swallow boric acid.