At a glance

  • Trichomoniasis ("trich") is an infection caused by tiny parasites that are spread through sex.
  • The symptoms include discharge and a burning sensation when peeing, especially in women.
  • The infection can be treated effectively with antibiotics.
  • It may lead to complications if left untreated.
  • It is important that sexual partners have treatment at the same time.


Photo of woman taking tablets

Trichomoniasis ("trich") is a sexually transmitted (STI). It is caused by single-celled parasites that particularly infect the mucous membranes lining the urethra (urine tube) and vagina.

The often goes unnoticed. Men only rarely have symptoms. Typical symptoms in women are pain when peeing, and an unusual vaginal discharge. The internal sex organs may also become infected if trichomoniasis is left untreated. That can lead to infertility in women.

Taking the antibiotic metronidazole is usually enough to effectively kill the parasites. To prevent re-infection, it's important that sexual partners also get treatment at the same time.


Trichomoniasis symptoms typically include a burning sensation and pain when peeing. In women, the vagina may be red and itch, and sex can be painful. There might also be a frothy, yellowish brown discharge that smells foul and unpleasant.

Trichomoniasis doesn't cause any symptoms in a lot of people. In fact, symptoms are more of an exception in men. But even if people don’t have symptoms, they can still pass on the disease during sex.

Causes and risk factors

The is caused by single-celled parasites that particularly infect the mucous membranes lining the urethra (urine tube) and vagina. The medical term for this parasite is “Trichomonas vaginalis.” But the parasites can also cause inflammations of the cervix, the bladder and (more rarely) the rectum.

Trichomonas parasites don't survive very long outside the human body. So people usually only become infected through direct contact with mucous membranes during sex. People who regularly have sex with different sexual partners and don't use a condom have a higher risk of getting trichomoniasis and other sexually transmitted infections.

It is possible to become infected from sharing a bath or through objects like toilet seats and towels, but that is rare. It is also rare for the to be passed on from a mother to her baby during birth.

Prevalence and outlook

Trichomoniasis infections are one of the most common sexually transmitted infections: It is estimated that over 250 million people are infected each year worldwide. The is diagnosed more frequently in women than in men. It is now thought to be less common in Germany and other countries, but there are no clear statistics here.

Trichomoniasis infections often go unnoticed. If people do have symptoms, then these develop about a week after on average. Some people already have symptoms after four days, and in others it can take up to three weeks. The can become chronic if left untreated – especially in women.

Whether you have symptoms or not: You are contagious for as long as you have the .


Complications may develop if the internal sex organs also become infected – such as the lining of the womb (endometrium), the fallopian tubes, and the ovaries in women. If that causes different areas of tissue to become stuck to each other (adhesions), the risk of ectopic pregnancies and infertility increases.

In men, the prostate gland, testicles and epididymis may become infected. It is not clear whether this decreases their .

Women with trichomoniasis have a higher risk of getting HIV because it is easier for the HIV viruses to enter the inflamed mucous membranes.

Trichomoniasis during pregnancy increases the risk of miscarriage or of the child being too small at birth.


The involves taking a swab from the inflamed mucous membranes. The doctor will use a cotton bud to take samples of the fluid and mucous membrane cells from the urethra, vagina, or possibly the anus. Those samples are tested in a laboratory to look for the parasite.

If the urethra is infected, that can also be diagnosed by taking a urine sample. A morning urine sample is best here.


It can be helpful to find out how sexually transmitted infections are passed on and what factors increase the risk. That helps to prevent them and decide whether and which preventive measures are a good idea. You can get information and advice about trichomoniasis and other STIs from sexual health clinics and doctors, such as specialists for dermatology and sexual health.

Condoms and femidoms (condoms for women) are a simple protective measure. But they do not provide complete protection against the parasites.

There is no proof that applying germicidal products to the vagina before sex can prevent trichomoniasis. No other measures are known to prevent it, either.

Prevention also means protecting others: If you have trichomoniasis, it is important not to have sex until you have finished your treatment. The same applies for taking baths together and sharing clothes or sex toys. It is also important that you inform everyone who you might have infected. Steady sex partners usually have treatment at the same time to avoid re-infecting each other (ping-pong effect).


Trichomoniasis can be treated with medication called metronidazole. This antibiotic not only effectively kills , but also kills single-celled parasites like Trichomonas vaginalis.

The treatment usually only takes one day in men, and seven days in women. The medication has to be prescribed by a doctor. It is taken in the form of tablets, often in the morning and evening. That is usually enough to effectively kill the parasites.

Longer treatment might be needed if the symptoms don't go away – perhaps combined with metronidazole vaginal suppositories.

Metronidazole has not been approved for use in pregnant women. But experts assume that it doesn't harm unborn babies. If treatment is needed, the medication can be taken ‘off-label’ in agreement with your doctor.

Deutsche STI-Gesellschaft (DSTIG). Sexuell übertragbare Infektionen (STI) – Beratung, Diagnostik und Therapie (S2k-Leitlinie). AWMF-Registernr.: 059-006. 2018.

Fode M, Fusco F, Lipshultz L et al. Sexually Transmitted Disease and Male Infertility: A Systematic Review. European Urology Focus 2016; 2(4): 383-393.

Graves KJ, Novak J, Secor WE et al. A systematic review of the literature on mechanisms of 5-nitroimidazole resistance in Trichomonas vaginalis. Parasitology 2020; 147(13): 1383-1391.

Henderson JT, Henninger M, Bean SI. Behavioral Counseling Interventions to Prevent Sexually Transmitted Infections: A Systematic Evidence Review for the U.S. Preventive Services Task Force. (AHRQ Evidence Syntheses; No. 192). 2020.

Masha SC, Cools P, Sanders EJ et al. Trichomonas vaginalis and HIV infection acquisition: a systematic review and meta-analysis. Sex Transm Infect 2019; 95(1): 36-42.

Nenoff P, Manos A, Ehrhard I et al. [Nonviral sexually transmitted infections-epidemiology, clinical manifestations, diagnostic workup, therapy. Part 3: Treponemes, Gardnerella and trichomonads]. Hautarzt 2017; 68(2): 136-148.

Obiero J, Ogongo P, Mwethera PG et al. Topical microbicides for preventing sexually transmitted infections. Cochrane Database Syst Rev 2021; (3): CD007961.

Pschyrembel Online. 2021.

Weyerstahl T, Stauber M. Duale Reihe Gynäkologie und Geburtshilfe. Stuttgart: Thieme; 2013.

Wiyeh AB, Mome RK, Mahasha PW et al. Effectiveness of the female condom in preventing HIV and sexually transmitted infections: a systematic review and meta-analysis. BMC Public Health 2020; 20(1): 319.

Workowski KA, Bachmann LH, Chan PA et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep 2021; 70(4): 1-187.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

Comment on this page

What would you like to share with us?

We welcome any feedback and ideas - either via our form or by We will review, but not publish, your ratings and comments. Your information will of course be treated confidentially. Fields marked with an asterisk (*) are required fields.

Please note that we do not provide individual advice on matters of health. You can read about where to find help and support in Germany in our information “How can I find self-help groups and information centers?

Print page

Über diese Seite

Created on January 2, 2023

Next planned update: 2025


Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

How we keep you informed

Follow us on Twitter or subscribe to our newsletter or newsfeed. You can find all of our films online on YouTube.