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:

^^ Back to top


Trichomoniasis can sometimes be difficult to diagnose because symptoms are similar to those of other sexually transmitted infections (STIs).

If you think you may have trichomoniasis, you should visit your GP or your local genitourinary medicine (GUM) clinic.

Find your nearest sexual health clinic.

Some GP surgeries offer an enhanced sexual health service for diagnosing and treating STIs. It may be better to visit a GUM clinic instead because these clinics can carry out accurate tests more quickly.

In some cases, your GP may refer you to a GUM clinic for tests and treatment if they think you have trichomoniasis.


If your doctor or nurse suspects you have trichomoniasis, they'll usually carry out an examination of your genital area.

In women, trichomoniasis may cause abnormal vaginal discharge or red blotches on the walls of the vagina and on the cervix (the neck of the womb).

If you are a man with suspected trichomoniasis, your doctor or nurse will examine your penis for signs of inflammation or discharge.

Laboratory testing

After a physical examination, your doctor or nurse may need to take a swab from either the vagina or penis. The swab will be analysed in a laboratory to check for signs of the trichomoniasis infection. It may take several days for the results to come back.

In men, a urine sample can also be tested for trichomoniasis.

If your doctor or nurse strongly suspects you have trichomoniasis, you may be advised to begin a course of treatment before your results come back. This ensures your infection is treated as soon as possible and reduces the risk of the infection spreading.

See treating trichomoniasis for more information.

Notifying sexual partners

If the test shows you have trichomoniasis, it's very important that your current sexual partner and any other recent partners are also tested and treated. The staff at the clinic or GP surgery can discuss with you which of your sexual partners may need to be tested.

If possible, tell your sexual partner and any ex-partners so they can get tested and treated as well. If you don't want to do this, the clinic can usually do it for you (it's called partner notification and the clinic won't reveal who you are).

If you've had trichomoniasis and have been cured, there's no need to tell any future partners.

^^ Back to top


Trichomoniasis is unlikely to go away without treatment. The infection may cure itself in rare cases, but you risk passing the infection on to someone else if you're not treated.


Trichomoniasis is usually treated quickly and easily with antibiotics.

Most people are prescribed an antibiotic called metronidazole which is very effective if taken correctly. You'll usually have to take metronidazole twice a day, for five to seven days.

Sometimes this antibiotic can be prescribed in a single, larger dose. However, this may have a higher risk of side effects and it's not recommended for pregnant or breastfeeding women as a precaution.

Metronidazole can cause nausea, vomiting and a slight metallic taste in your mouth. It's best to take it after eating food. Contact your doctor for advice if you start vomiting, because the treatment won't be effective if you're unable to swallow the tablets.

Don't drink alcohol while taking metronidazole and for at least three days after finishing the course of antibiotics. Drinking alcohol while taking this medicine can cause more severe side effects, including:

  • a fast heartbeat or heart palpitations
  • skin flushing
  • nausea and vomiting

A specialist can recommend alternative treatments if metronidazole is unsuitable for you (for example, if you're allergic to it).


If you take your antibiotics correctly, you won't normally need any follow-up tests or examinations for trichomoniasis.

However, you may require further testing to see whether your symptoms are being caused by a different sexually transmitted infection (STI) if your symptoms remain or recur after treatment.

If you have unprotected sex before your treatment is finished, you need to return to your GP surgery or sexual health clinic. You may have become reinfected. You must also return if you:

  • didn't complete your course of antibiotics
  • didn't take your antibiotics correctly (according to the instructions)
  • vomited shortly after taking your antibiotics

You may need more antibiotics or a different form of treatment.

Sexual partners

You should avoid having sex while you're being treated for trichomoniasis, as you may become reinfected.

If you were prescribed a single dose of antibiotics, you need to avoid having sex for seven days after taking the medication.

It's very important that your current sexual partner and any other recent partners are also tested and treated. If your sexual partner isn't treated, this increases the risk of reinfection.

^^ Back to top


If you've had trichomoniasis and it's been treated, you won't be immune to the infection and could get it again.

Like any sexually transmitted infection (STI), the best way to prevent trichomoniasis is to have safe sex. This means always using a condom.

The following measures will help protect you from trichomoniasis and most other STIs, including chlamydia and gonorrhoea. They'll also help prevent you passing it on to your partner:

  • Use condoms (male or female) every time you have vaginal or anal sex.
  • If you have oral sex, cover the penis with a condom or the female genitals with a latex or polyurethane square (a dam).
  • If you're a woman and rub your vulva against your female partner's vulva, one of you should cover your genitals with a dam.
  • Avoid sharing sex toys. If you do share them, wash them or cover them with a new condom before anyone else uses them.

If you're not sure how to use condoms correctly, you can read about how to use a condom.

If you've been diagnosed with trichomoniasis, make sure both you and your partner are treated, and that any sex toys you've used are cleaned.

Getting tested

If you're sexually active, go for regular sexual health check-ups. You can get an appointment by visiting your local genitourinary medicine (GUM) clinic.

Find your local sexual health clinic.

If you notice any signs or symptoms of an STI, avoid having sex and visit your GP or GUM clinic as soon as possible.

^^ Back to top

The information on this page has been adapted by NHS Wales from original content supplied by NHS Choices.
Last Updated: 19/01/2016 09:24:34