Woman with vaginatis in black and white

The vagina remains in good health if things remain stable and friendly, but since it exposes an internal part of a woman’s body to the outside world, it is at risk for infection. Vaginitis is the word used to describe an irritation of the vagina.

The most common three conditions resulting in vaginitis are, in order of frequency:

  1. Bacterial vaginosis (BV)—from bacteria
  2. Yeast vaginitis—from fungus
  3. Trichomonas vaginitis—from a protozoan

When it is a bacterial infection, this usually entails a change in the vagina’s internal environment, swapping out the beneficial lactobacilli for an overgrowth of the invader. It is the good lactobacilli bacteria of the vagina which help it maintain its acidic environment so it will be hostile to infections, except for yeast.

Yeast vulvovaginitis

I explore this ahead of the others, because yeast infection is the first thing suspected by a woman when she begins symptoms that involve burning, itching, redness, and painful irritation. But these symptoms can occur with all types of vaginitis, and the fact that yeast infection is only the second-most common vaginal infection means the first impression is wrong. (The most common infection is bacterial vaginosis, below.)

This is not the only source of confusion. The most frequent species of yeast, Candida, can be part of the vagina’s normal flora in up to 20% of women1. Therefore, true yeast vaginitis is only when there is associated irritation of the vulva and vagina (vulvovaginitis). This also makes one wonder if this is an actual infection in these women: a better interpretation might be that it’s an overgrowth2.

Yeast is everywhere. It’s on people’s shoes, clothes, shower curtains, furniture, pets, etc. It’s in every room of a person’s house. It is also in the rectum as a normal inhabitant. When a woman has a vaginal yeast infection, it’s usually because yeast has crossed over from her rectum/anus to her vagina. Sex, wiping, and even roofing over these areas with underwear can cause this to happen. It is quite accidental. It can also be delivered through sexual intercourse, even from the man’s rectum.

Regardless, if yeast is identified along with a woman’s symptomatic vulvovaginitis, it should prompt treatment. True, it won’t kill her, but it will continue to be painful, interfering with her quality of life, sexual activity, and even employment. It can even affect the tissue such that it is susceptible to a bacterial superinfection, such as with strep or staph.

Identifying yeast as the culprit involves determining the pH of the vagina (4-4.5 with yeast) and looking at the discharge under the microscope, called a wet mount. A wet mount can demonstrate yeast as well as show other conditions that might rule yeast out.

Treatment is with antifungal vaginal suppositories and cream (miconazole: Monistat), or oral medications (fluconazole: Diflucan)3. Such vaginal applications use harsh chemicals, so if a woman cannot tolerate these, the oral antifungals are indicated.

Bacterial vaginosis (BV)

BV, contrary to what is commonly thought about yeast, is the most common type of vaginal infection. It constitutes half the cases. The symptoms can be the same as yeast, but a pH and wet mount can make the distinction, because yeast is in an acid environment, but BV is in an alkaline environment. It is often without symptoms, hence being called bacterial vaginosis, not bacterial vaginitis, and up to 75% of women with BV are without symptoms. The vaginosis of BV is not sufficient to cause symptoms of vaginitis, but usually requires a second pathogen which the BV makes more likely.

BV is different from yeast in that it is a bacterium, not a fungus. Its invasion into the vaginal flora creates a change in the environment. Besides making ammonia-like breakdown products that are irritating and malodorous, the invading bacteria also place a thin biofilm on the vaginal tissue that attracts other types of bacteria which can make the vaginosis progress to vaginitis.

Although sex is a risk factor for BV, it is not considered, officially, an STD. It is often associated, however, with the presence of other STDs, such as herpes simplex.

BV is diagnosed with

  • pH greater than 4.5.
  • smell of a fishy odor when potassium hydroxide is added to a sample on the wet mount—a famous, time-honored diagnostic test called the whiff test.
  • presence of Clue cells—when 1 out of 5 vaginal cells show bacteria hanging off of them.

Treatment is with antibiotic cream, gel, or pills, either with metronidazole (Flagyl) or with clindamycin4, both OK in pregnancy.


Trichomonas is not a bacterial or yeast infection. It is an infection of by a protozoan called Trichomonas vaginalis. Of the three types of vaginal infection, this one is always a sexually transmitted disease (STD). Direct observation of a flagellated organism swimming around under the microscope is the best way to diagnose, as the pH (5-6) could be in the range seen with BV. In fact, it is common for a woman who has Trichomonas to have BV as well. The flagellated organisms are very easy for the healthcare provider to see, moving around very energetically in real time.

Unlike BV, men can have symptoms with Trichomonas. It can present with prostatitis, a penile discharge, and even infertility or a higher risk for cancer.

Untreated, BV can progress to involve the urethra and bladder. It can also increase a woman’s susceptibility to HIV twice the norm. In pregnancy, it can provoke premature birth due to premature rupture of membranes. Newborns of infected mothers can get it from them.

Treatment is by the use of antibiotics, usually metronidazole (Flagyl)5.

Bacterial vaginosis can exist without symptoms and 20% of women normally carry yeast as a normal part of their vaginal flora. When BV is seen incidentally in the doctor’s office, it should be treated with a pre-emptive strike before it turns into vaginitis. Trichomonas, on the other hand, requires treatment of both a woman (especially if pregnant) and her partner (male or female) with a follow-up check to ensure its eradication.

These three—the most common sources of vaginitis—are not the last word. There are other conditions that can mimic these or make them difficult to treat. Stay tuned!

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  1. Goldacre MJ, Watt B, Loudon N, et al. Vaginal microbial flora in normal young women. Br Med J 1979; 1:1450.
  2. Sobel JD. Epidemiology and pathogenesis of recurrent vulvovaginal candidiasis. Am J Obstet Gynecol 1985; 152:924.
  3. https://www.uptodate.com/contents/candida-vulvovaginitis?source=search_result&search=vaginitis&selectedTitle=3~150#H13
  4. https://www.uptodate.com/contents/bacterial-vaginosis-treatment?source=related_link
  5. https://www.uptodate.com/contents/trichomoniasis?source=search_result&search=trichom

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