Sexual health

Trichomoniasis: symptoms, testing and treatment

Trichomoniasis is the most common curable STI and often has no symptoms. Discharge, how it spreads, testing, treatment, partners and when to have sex again.

✓ Reviewed by the editorial team · Updated 15 October 2026

Trichomoniasis ("trich") is a sexually transmitted infection caused by a tiny parasite called Trichomonas vaginalis. It can be cured with a short course of tablets. It is the most common curable STI in the world: the World Health Organization (WHO) estimates there were around 156 million new infections in people aged 15 to 49 in 2020.

What it is and what causes it

Trichomonas vaginalis is a protozoan: a single-celled organism that moves with tiny whip-like threads. It is neither a bacterium nor a virus. It lives in the genital and urinary tract. In women it mainly affects the vulva, vagina, cervix and urethra. In men it mainly affects the urethra, inside the penis.

Symptoms and when they appear

Most people notice nothing. According to the CDC, around 70% have no symptoms, especially men. When symptoms do appear, they usually start 5 to 28 days after infection, though sometimes much later, and they can come and go.

In the vulva and vagina you may notice:

a change in discharge: more of it, sometimes yellow-green, frothy or strong-smelling;
itching, soreness, redness or irritation;
discomfort or burning when you pee;
discomfort during sex. If that sounds familiar, see also our article on pain during sex.

With a penis, you may have stinging when you pee or after ejaculating, needing to pee often, a slight discharge or irritation. These symptoms look like those of other STIs or vaginal thrush, so only a test can tell.

How it spreads – and how it doesn't

It is mainly passed on through vaginal sex without a condom (penis to vagina), and also between vulvas through direct genital contact. Sharing sex toys without washing them or changing the condom can pass it on too. Infection of the mouth or anus is uncommon.

It can be passed on even without symptoms. And having had it before doesn't protect you: you can get it again.

It is not spread by kissing, hugging, swimming pools, towels, cutlery or toilet seats.

Key point: trichomoniasis is very common, often causes no symptoms and is easy to cure. Having it says nothing bad about you; what matters is getting tested and treated, together with your partner.

Testing: when and how

Symptoms alone can't confirm trich. You need a lab test, and it's simple:

a swab from the vagina (you can often take it yourself) or from the penis;
or a urine sample.

The most sensitive tests look for the parasite's genetic material (NAAT/PCR). If you have symptoms, get checked as soon as you notice them. If you don't, but there has been a risk, ask your clinic when to test; if you test very early and it is negative, they may suggest repeating it. It's a good idea to test for HIV, syphilis and other STIs at the same visit. Read more in how often to get tested for STIs.

Treatment: it can be cured

It is treated with an antibiotic that acts against the parasite, taken as tablets, either as a single dose or over several days, as your clinician advises. It works very well. Symptoms usually improve within a few days, but you must finish the whole course. Alcohol is best avoided with some of these medicines: ask at the clinic or pharmacy.

When can you have sex again? Wait until you and your partners have all finished treatment and your symptoms have gone. The NHS advises waiting at least one week after everyone has finished.

Treating partners and retesting

Your current and recent sexual partners also need treatment, even if they feel fine. Otherwise the infection can easily come back the next time you have sex (the "ping-pong" effect). The clinic can help you tell them, even without giving your name.

According to the CDC, around 1 in 5 people get infected again within 3 months. That's why a repeat test about 3 months after treatment is recommended.

Key point: treating everyone involved at the same time, waiting before having sex again and retesting at 3 months is what stops reinfection.

Complications and pregnancy

Without treatment, the infection can last for months or even years. It can also:

cause genital inflammation that makes it easier to get or pass on HIV; WHO puts the risk at around 1.5 times higher;
be linked to pelvic inflammatory disease and bacterial vaginosis in women;
cause inflammation of the prostate in men.

In pregnancy, untreated trich is linked to early birth, waters breaking early and low birthweight. The tablets are safe in pregnancy, so if you are pregnant and have symptoms or a possible risk, mention it as soon as you can. There is more in our pregnancy and postpartum guide.

Prevention

Using a condom correctly every time you have sex is the most effective step.
Wash sex toys or cover them with a new condom for each person.
Get tested regularly if you have new or several partners, and talk about STIs before sex.
Make sure all partners are treated at the same time if the infection is found.

There is no vaccine against trichomoniasis.

When to get help

See your GP, a sexual health clinic or a gynaecologist if:

you notice a change in discharge, itching, soreness or a strong genital smell;
it stings when you pee or you have discharge from the penis;
a partner tells you they have trich or another STI;
you are pregnant and may have been at risk;
your symptoms carry on after treatment.

It's a routine appointment. You'll be seen without judgement, and in most cases it's sorted within a few days.