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Trichomoniasis is a sexually transmitted infection (STI) caused by a tiny parasite called Trichomonas vaginalis, or TV, which infects the vagina and the urethra in both men and women.

Here are some key facts:

  • 50% of men and women don’t experience symptoms 
  • If symptoms do appear, soreness, swelling and itchiness is common in the vagina and head of the penis. Women can also experience a fishy-smelling discharge that may be yellow-green, thick, thin or frothy. Men can also experience pain during ejaculation or urination and thin white discharge. 
  • Diagnosing trichomoniasis is tricky because its symptoms are similar to that of other STIS but it can be tested for by taking a swab 
  • Trichomoniasis can be passed on through unprotected vaginal sex or sharing sex toys 
  • Without treatment, the infection can last for months but is easily treated with antibiotics
  • It can be serious during pregnancy as it may increase the risk of complications such as premature birth

You can read about trichomoniasis in more detail below.

Signs and symptoms of trichomoniasis

Up to half of men and women with trichomoniasis will not experience any symptoms and when symptoms do appear, they are often easily confused with other STIs. 

If symptoms do appear, it will usually be within a month of coming into contact with the infection.

Symptoms in women can include:

  • Vaginal itching, swelling and soreness
  • A discharge that is unusual for you. It can be frothy and yellow-green coloured and can smell fishy
  • Lower abdominal pain (tummy)
  • Pain during sex and while weeing
  • Itchy inner thighs (in women)

Symptoms in men can include:

  • Thin, white discharge from the penis
  • Pain during ejaculation and while weeing
  • Itching, swelling and soreness of the penis
  • Needing to wee more often

The causes and how it is passed on

Trichomoniasis is an infection caused by a parasite called Trichomonas vaginalis, or TV. The infection affects the vagina and the urethra (the tube that carries urine from the bladder out of the body) in men and women. 

It is easily passed on through having unprotected vaginal sex or sharing sex toys. 

It is not known whether it can be passed on by genital contact or by transferring discharge from one vagina to another on the fingers.

It doesn’t matter if you’ve had one sexual partner or a hundred, trichomoniasis can affect anyone who is sexually active.

You cannot get trichomoniasis from hugging, kissing, sharing cups, plates or cutlery and toilet seats.

Testing for trichomoniasis

Diagnosing trichomoniasis is not easy as its symptoms are similar to other STIs. If a doctor or nurse examines you, they will be looking for signs of the infection which include red patches on the walls of the vagina and in men, discharge, swelling and soreness from of the head of the penis.

To be sure of what it is, they will also take a swab from your vagina or penis which will be tested for signs of the infection. A swab is taken by brushing a sort of cotton bud or a small plastic loop over the inside of the vagina and head of the penis. It may be a little uncomfortable but shouldn’t be painful. In men, trichomoniasis can also be tested by taking a urine sample.

It may be that the sexual health service that you are visiting is able to do a test which produces the results during the appointment time (this is called 'point of care testing'). Or they make take a swab and then look at the sample under a microscope in order to diagnose it during your visit.  Otherwise the swab may be sent away to a lab, in which case the results normally take a week to come back. 

If there is a high chance that you have trichomoniasis (for example if your partner has tested positive), you may be given treatment before the results are back. But be aware that even if your partner tested negative, you could still have it.

You can be tested for trichomoniasis at Brook services, your GP surgery or at GUM or sexual health clinics

Treatment of trichomoniasis

Trichomoniasis is unlikely to go away by itself but is easily treated with antibiotics. You will often be prescribed an antibiotic called metronidazole which you take for five to seven days.

Metronidazole is very effective but it can make you feel sick and it can’t be mixed with alcohol. In fact, you should wait until 48 hours after finishing your course. The doctor or nurse who prescribes your treatment will advise you further.

Trichomoniasis is not serious unless you are pregnant when it can cause complications. But don’t worry, it can still be safely treated. Make sure you inform the doctor or nurse if you are (or think you are) pregnant so that they can take this into consideration.

If you had symptoms, you should notice improvements quite quickly. You should go back to where you had your test if:

  • The symptoms don’t improve within a week
  • You have unprotected sex again
  • You had unprotected sex with your partner before the treatment was finished
  • You did not follow the instructions or complete the treatment
  • You vomited after taking the antibiotics
  • The test was negative but you develop signs and symptoms of trichomoniasis

You should also avoid having sex until you have been given the all-clear, to prevent you being re-infected or passing the infection on.

It is important that you tell your current and any recent sexual partners that you are being treated for trichomoniasis, so that they go for treatment too. In the UK it is recommended you tell any sexual partners you have had over the last six months.

The staff at Brook or sexual health clinics can help if you find it hard to talk to them about trichomoniasis.

Some clinics may also offer to contact your partner using what’s called a ‘contact slip’. This is to warn them they may have been exposed and to recommend they get tested and it doesn’t mention your name.

Be mindful of the fact that you will not be protected from trichomoniasis after treatment and you could get it again.

Page last reviewed: September 2015
Next review due: September 2017