Trichomoniasis is a sexually transmitted infection (STI) caused by a tiny parasite called Trichomonas vaginalis (TV).

Symptoms of trichomoniasis usually develop within a month of infection, although up to half of all infected men and women have no symptoms.

The symptoms of trichomoniasis are similar to those of many other sexually transmitted infections (STIs) so it can sometimes be difficult to diagnose.

Symptoms in women

Trichomoniasis in women can cause any of the following symptoms:

  • abnormal vaginal discharge that may be thick, thin or frothy and yellow-green in colour
  • producing more discharge than normal, which may also have an unpleasant fishy smell
  • soreness, inflammation (swelling) and itching around the vagina – sometimes the inner thighs also become itchy
  • pain or discomfort when passing urine or having sex

Symptoms in men

Trichomoniasis in men can cause any of the following symptoms:

  • pain during urination or ejaculation
  • needing to urinate more frequently than usual 
  • thin white discharge from the penis
  • soreness, swelling and redness around the head of the penis (balanitis) or foreskin (balano-posthitis)

When to seek medical advice

Visit your GP or local genitourinary medicine (GUM) clinic if you develop any of the symptoms of trichomoniasis or if you think you may be infected.

Trichomoniasis can usually be diagnosed after an examination of the genitals and a laboratory test carried out on a swab taken from the vagina or penis.

If the test shows you have trichomoniasis, it's important that your current sexual partner and any other recent partners are also tested and treated.

Read more about diagnosing trichomoniasis.

How do you get trichomoniasis?

Trichomoniasis is caused by a tiny parasite called Trichomonas vaginalis.  

In women, this parasite mainly infects the vagina and urethra (tube that carries urine out of the body). In men, the infection most commonly affects the urethra, but the head of the penis or prostate gland (a gland near the bladder that helps produce semen) can become infected in some cases.

The parasite is usually spread by having unprotected sex (sex without a condom). It could also be spread by sharing sex toys if you don't wash them or cover them with a new condom before use.

You don't have to have many sexual partners to catch trichomoniasis. Anyone who is sexually active can catch it and pass it on.

Trichomoniasis isn't thought to be passed on through:

  • oral or anal sex
  • kissing or hugging
  • sharing cups, plates or cutlery
  • toilet seats

The best way to prevent trichomoniasis is to have safer sex. This means always using a condom when having sex, covering any sex toys you use with a condom, and washing sex toys after use.

Read more about preventing trichomoniasis.

Treating trichomoniasis

Trichomoniasis is unlikely to go away without treatment, but it can be effectively treated with antibiotics. Most men and women are treated with an antibiotic called metronidazole, which is usually taken twice a day for five to seven days.

It's important to complete the whole course of antibiotics and avoid having sex until the infection clears up, to prevent reinfection.

Your current sexual partner and any other recent partners should also be treated.

Read more about treating trichomoniasis.

Complications of trichomoniasis

Complications of trichomoniasis are rare, although some women with the infection may be at an increased risk of further problems.

If you're infected with trichomoniasis while you're pregnant, the infection may cause your baby to be either: 

Page last reviewed: 08/12/2015

Next review due: 08/12/2017