What Is It?

Trichomoniasis is the most common curable sexually transmitted disease (STD) in the United States. Infected women may experience a frothy, yellow-green vaginal discharge with a strong odor, discomfort during intercourse and urination, or itching in the genital area.

Maybe you haven't heard of this infection. It is the stepchild of sexually transmitted diseases—one that is hard to pronounce, let alone find information about why it is important.

Ironically, trichomoniasis (trick-o-mon-i-a-sis or "trich") is the most common curable sexually transmitted disease (STD). In recent years, diagnosing and treating this disease has received more attention as new research has shown that it is not as harmless as was once thought.

About 3.7 million people have trichomoniasis, according to the U.S. Centers for Disease Control and Prevention (CDC). Most men infected with the parasite Trichomonas have no symptoms. When symptoms occur, men may experience irritation inside the penis, discharge or slight burning after urination or ejaculation. Most women are also asymptomatic. Some women with the infection experience a frothy, yellow-green vaginal discharge with a strong odor, discomfort during intercourse, pain during urination, itching in the genital area or spotting between periods. In rare cases, pain in the lower abdomen can occur. Women infected with Trichomonas are more at risk of acquiring human immunodeficiency virus (HIV) and other STDs.

Because trichomoniasis is so common and causes significant risks to women's health, you would expect to see more interest in its prevention. There are several reasons why this STD has received so little attention. First, its symptoms—primarily discharge and irritation of the vagina and urethra— are mild and have been seen as troubling but less serious than the side effects of other STDs. Second, the most common treatments—metronidazole and tinidazole—are highly effective in most women, though some difficulties can arise, such as drug allergies or intolerance or Trichomonas becoming resistant to this class of drugs. No other class of drugs is very effective for treatment.

The organisms that cause trichomoniasis are protozoans (the simplest, single-cell organism in the animal kingdom). These protozoans, called trichomonads, can infect other areas of the body, but Trichomonas vaginalis is responsible for genital infection and vaginitis. This parasite resides primarily in the vagina and/or bladder, where body temperature, low oxygen environment and moisture allow it to grow and multiply.

Trichomoniasis is one of the three most common types of vaginitis. The other types are bacterial vaginosis (BV), which is an overgrowth of anaerobic bacteria found in the vagina, and vulvovaginal candidiasis, more commonly known as yeast infection.

As with BV, some research suggests that trichomoniasis is associated with preterm birth. Women infected with Trichomonas during pregnancy are more likely to have low birth weight babies (less than 5.5 pounds).

Studies also link trichomoniasis with an increased risk of HIV transmission (HIV is the virus that leads to AIDS). Studies show that women infected with this STD are at higher risk of acquiring and transmitting HIV.

Trichomoniasis is transmitted through sexual intercourse. It is most common in people who are at their peak of sexual activity (teens and 20s), but it is found in higher rates among older women than other STDs. Having multiple sex partners and infection with other STDs are primary factors that increase a woman's risk of infection.

In very rare cases, trichomoniasis may be transmitted by a pregnant woman to her baby during childbirth. Pregnant women with trichomoniasis are more likely to deliver early and to give birth to a low birth-weight baby (less than 5.5 pounds). Their babies are also more likely to have conjunctivitis.

In the United States, about 3 percent of women are infected. Among women infected with other STDs, such as gonorrhea, the rate of trichomoniasis is higher. For reasons not entirely clear, African American women are 5 to 10 times more likely have trichomoniasis than Hispanic or Caucasian women.


A significant number of women infected with trichomoniasis have no noticeable symptoms. If symptoms develop, they usually occur within five to 28 days after exposure to an infected partner. However, in some cases, the symptoms may be delayed for longer. The most common symptoms are vaginal discharge, irritation, itching and burning during urination.

Trichomoniasis most often presents as a yellowish-green vaginal discharge with a strong odor. Itching and soreness of the vagina and vulva are common. Some women experience vague abdominal pain. Trichomoniasis can occur with other infections, particularly pelvic inflammatory disease and bacterial vaginosis.

The majority of men infected with Trichomonas do not have symptoms. The most common symptom is discharge from the penis or burning with urination. When men have symptoms, they often subside without treatment after a week or more.

For both men and women, a diagnosis based on symptoms is inadequate because many of these symptoms are shared with other inflammatory conditions of the vagina and cervix, such as bacterial vaginosis and yeast infections.

For women, the most common way to diagnose trichomoniasis is by physical examination of the pelvic area by a health care professional and by looking at a sample of vaginal fluid under a microscope (called "wet mounts") for the presence of protozoa. A pelvic examination can reveal small red ulcerations on the vaginal wall or cervix. The wet mount technique, however, is accurate only about 60 percent to 70 percent of the time, as protozoa may be hard to find or mistaken for normal cells. It can also yield false positives. There also are several rapid-diagnostic kits available that can diagnose infection in 10 to 45 minutes. These tests also come with the risk of false positives.

More reliable tests have been developed, such as the polymerase chain reaction (PCR) test, a type of nucleic acid test that uses enzymes to better detect the virus in the culture. It is very effective in identifying T. vaginalis in women and is becoming more readily available.


The standard drugs used for treating trichomoniasis are metronidazole (Flagyl) and tinidazole (Tindamax). In most cases, Trichomonas infection is cured in women with a single oral dose of two grams of either drug. Both of these prescription drugs are in the nitroimidazole class. Metronidazole has been found to be safe in pregnancy.

All sexual partners of an infected person should be treated. An infected person should abstain from sex during treatment and until all symptoms go away, approximately a week or two after treatment. Because of the high rate of reinfection (up to 17 percent within three months), sexually active women may want to consider getting rescreened three months after treatment. This is especially important for HIV-infected women who also have trichomoniasis, because they have an even higher rate of recurrence.

For those who fail treatment, longer courses of metronidazole or tinidazole are recommended by the Centers for Disease Control and Prevention (CDC). Patients who continue to have an infection after a single dose of metronidazole should take 500 milligrams of metronidazole orally twice a day for seven days. If this second course of medication fails, the CDC says to consider treating with two grams daily for five days of either metronidazole or tinidazole. If these therapies fail to cure the infection, further treatment should be discussed with a specialist.

You should take metronidazole or tinidazole with food and avoid drinking alcohol for 24 to 72 hours after taking the drugs.


Prevention of trichomoniasis is similar to that for other sexually transmitted diseases (STDs). Protective measures include:

  • Use a latex condom every time you have sex.
  • Limit your number of sex partners.
  • Get tested if you think you have an STD and have your partner tested, too.

Facts to Know

  1. Trichomoniasis is the most common curable sexually transmitted disease in the United States. According to the CDC, about 3.7 million people in the United States have trichomoniasis.
  2. Trichomoniasis is more common among African American women. The reason for this is not clear. Lack of access to medical care in economically challenged communities may play a role.
  3. Trichomoniasis increases a woman's risk of preterm birth or delivery of a low birth weight baby.
  4. It is important that sexual partners of infected women be treated. Although trichomoniasis is often asymptomatic in males, if left untreated it can cause urethral infections, particularly urethritis, and can lead to reinfection of the woman.
  5. Because a test for vaginal infection is not necessarily a part of a routine pelvic exam, you can't assume your health care professional will test you for trichomoniasis. You should request trichomoniasis screening if you have symptoms or if you have been in contact with a high-risk sexual partner.
  6. You can have more than one type of vaginitis at the same time. It is possible to have trichomoniasis and bacterial vaginosis together, each of which can be treated with metronidazole.
  7. If you visit your health care professional to see if you have a vaginal infection, you should schedule your examination when you are not having your period.
  8. It is easy to misdiagnose trichomoniasis or bacterial vaginosis as a yeast infection because yeast infection also causes an unpleasant discharge. Treatment for yeast infections is different than for trichomoniasis or BV, so an accurate diagnosis is important.

Questions to Ask

Review the following Questions to Ask about trichomoniasis so you're prepared to discuss this important health issue with your health care professional.

  1. Do over-the-counter products work for treating and preventing trichomoniasis?
  2. Does my partner need to be treated?
  3. What difference does it make whether I have trichomoniasis or a yeast infection?
  4. If I have had trichomoniasis in the past and am pregnant, should I get tested for it even if I have no symptoms?
  5. How do I identify trichomoniasis and avoid it in the future?
  6. Do I need to refrain from sexual contact while I am being treated?
  7. Will poor hygiene increase my risk of trichomoniasis?
  8. Can trichomoniasis be passed on to my baby?
  9. Are the drugs used for treating trichomoniasis safe for pregnant women?
  10. What happens if I am infected with trichomoniasis but never get treated? Will it go away on its own?

Key Q&A

How do I know if I need to see my health care professional?

Pay attention to your body. Call your health care professional if you experience any unusual symptoms, such as: a change in the color, odor or consistency of vaginal fluid; vulvar irritation; itching; and burning, frequent or painful urination.

What if I am allergic to the 5-nitroimidazole drugs (metronidazole or tinidazole) or am not responding well to them?

Up to 10 percent of women do not respond to standard treatment. For those who fail treatment, a longer course of metronidazole is recommended by the Centers for Disease Control and Prevention (CDC). If this second course of medication fails, the CDC recommends two grams daily for five days of either metronidazole or tinidazole.

If you develop a rash in response to the 5-nitroimidazole drugs, there are other medications you can try, but they have poor cure rates. If you are allergic to tinidazole and metronidazole, your provider may suggest desensitizing you to these medications so you can undergo treatment.

What are my chances of having trichomoniasis reoccur?

Treatment is successful in most women, and once the organisms are killed they don't come back unless you are exposed again to an infected partner.

What is the relationship between vaginitis and excessive douching?

The healthy vaginal ecosystem requires just the right balance of bacteria flora. These bacteria make natural acids that keep abnormal bacteria from becoming predominant. Douching may disrupt the pH balance of the vagina and lead to bacterial vaginosis, which may increase a woman's risk of acquiring trichomoniasis.

What about diagnosing and treating trichomoniasis in men?

The organisms that cause trichomoniasis often don't cause symptoms in males. Consequently, most men never seek treatment because they don't know they are infected. Diagnosis in men is usually made with a urine culture specifically for Trichomonas. If your sexual partners are not treated, it is likely you will become reinfected.

What is considered normal vaginal discharge?

For uninfected women, vaginal discharge is usually cloudy white in appearance. Discharge often increases in the middle of your menstrual cycle, and during ovulation it changes consistency, appearing similar to egg whites. Symptomatic women with trichomoniasis experience a frothy, yellow-green vaginal discharge with a strong odor, possibly coupled with discomfort during intercourse, painful urination or genital itching.

Organizations and Support

For information and support on coping with Trichomoniasis, please see the recommended organizations, books and Spanish-language resources listed below.

American College of Obstetricians and Gynecologists (ACOG)
Website: https://www.acog.org
Address: 409 12th Street, SW
P.O. Box 96920
Washington, DC 20090
Phone: 202-638-5577
Email: resources@acog.org

American Social Health Association (ASHA)
Website: https://www.ashasexualhealth.org/
Address: P.O. Box 13827
Research Triangle Park, NC 27709
Hotline: 1-800-227-8922
Phone: 919-361-8400
Email: info@ashastd.org

ASHA's STI Resource Center Hotline
Website: https://www.ashasexualhealth.org/person2person-2/
Address: American Social Health Association
P.O. Box 13827
Research Triangle Park, NC 27709
Hotline: 1-800-227-8922
Phone: 919-361-8400

CDC National Prevention Information Network
Website: https://www.cdcnpin.org
Address: P.O. Box 6003
Rockville, MD 20849
Hotline: 1-800-458-5231
Phone: 404-679-3860
Email: info@cdcnpin.org

Guttmacher Institute
Website: https://www.guttmacher.org
Address: 1301 Connecticut Avenue NW, Suite 700
Washington, DC 20036
Hotline: 1-877-823-0262
Phone: 202-296-4012
Email: info@guttmacher.org

National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention
Website: https://www.cdc.gov/nchhstp
Address: Centers for Disease Control and Prevention
1600 Clifton Road
Atlanta, GA 30333
Hotline: 1-800-CDC-INFO (1-800-232-4636)
Email: cdcinfo@cdc.gov

Sexuality Information and Education Council of the United States (SIECUS)
Website: https://www.siecus.org
Address: 90 John Street, Suite 704
New York, NY 10038
Phone: 212-819-9770


Sexual Health Questions You Have...Answers You Need
by Michael V. Reitano and Charles Ebel

Sex: What You Don't Know Can Kill You
by Joe S. McIlhaney and Marion McIlhaney

Organizations and Support

Medline Plus: Trichomoniasis
Website: https://www.nlm.nih.gov/medlineplus/spanish/trichomoniasis.html
Address: US National Library of Medicine
8600 Rockville Pike
Bethesda, MD 20894
Email: custserv@nlm.nih.gov

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