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Trichomoniasis is a sexually transmitted infection (STI).


It is caused by a parasite. It passes between people during sex.

Risk Factors

It is more common in women than men. The risk may be higher for those who:

  • Have many sex partners
  • Do not use condoms with sex
  • Have had STIs before


The infection does not always cause symptoms. When they happen, they may be:

In women:

  • A bad-smelling, greenish-yellow discharge from the vagina
  • Pain, itching, or burning of the genitals
  • Bleeding after sex

In men:

  • Discharge from the penis
  • Itching or pain
  • Pain when passing urine
  • Pain in the testes or scrotum


The doctor will ask about your symptoms, and sexual and health history. A physical exam will be done. It will focus on the pelvic area.

Testing involves:

  • Women—testing fluid or discharge from the vagina
  • Men—testing urine, semen, or discharge from the penis

A lab will check the samples for the parasite.


The infection is treated with antibiotics. Sex partners may also need treatment.


The risk of STIs is reduced by:

  • Always using condoms during sex
  • Only having sex with one person

Centers for Disease Control and Prevention

The American Congress of Obstetrics and Gynecology


Sex & U—The Society of Obstetricians and Gynaecologists of Canada

The Sex Information & Education Council of Canada


Mercer F, Johnson PJ. Trichomonas vaginalis: pathogenesis, symbiont interactions, and host cell immune responses. Trends Parasitol. 2018;34(8):683-693.

Sexually transmitted diseases. National Institute of Allergy and Infectious Diseases website. Available at: https://www.niaid.nih.gov/diseases-conditions/sexually-transmitted-diseases. Accessed February 3, 2021.

Trichomoniasis. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/std/trichomonas/STDFact-Trichomoniasis.htm. Accessed February 3, 2021.

Trichomoniasis. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/trichomoniasis. Accessed February 3, 2021.

Last reviewed September 2020 by David L. Horn, MD, FACP  Last Updated: 2/3/2021