Trichomoniasis — what it is and how it's treated
Reviewed by the My London Pharmacy clinical team, Zaynab Ali, Pharmacist Independent Prescriber
·29 July 2026
·8 min read
Quick answer
Trichomoniasis is a common STI caused by a tiny parasite. It can cause discharge, itching or discomfort, though many people have no symptoms. It is diagnosed with a swab or urine sample and treated effectively with a course of antibiotics. Partners need treating too, and it is simple to clear once identified.
What trichomoniasis is
Trichomoniasis, often shortened to trich, is a sexually transmitted infection caused by a tiny parasite called Trichomonas vaginalis. It is passed on through unprotected vaginal sex and by sharing sex toys that have not been washed or covered with a fresh condom between uses. It mainly affects the vagina in women and the urethra, the tube that carries urine, in men. It is not passed on through everyday contact such as kissing, hugging, sharing towels, cups or toilet seats, and it is not caught from swimming pools, so there is no need to worry about the ordinary situations of daily life.
It is a common and very treatable infection, and although the word parasite can sound alarming, this is nothing to be frightened of once it is diagnosed. The organism is microscopic and simply lives in the moist tissues of the genital tract. Because symptoms are often mild or entirely absent, trichomoniasis can be present for weeks or months without being noticed, and it can be passed on during that time without either person realising. This is exactly why testing when you have symptoms or a possible exposure is so useful: catching it means it can be cleared quickly and simply, and the chain of transmission stopped.
Symptoms in women and men
Around half of people with trichomoniasis have no symptoms at all, which is one reason it can go undetected. When symptoms do occur, they often develop within a month of infection, though they can appear sooner or later than that.
In women, symptoms can include a change in vaginal discharge, which may become thicker, thinner or frothy and yellow-green with a noticeable, sometimes fishy, smell, along with soreness, swelling and itching around the vagina, and discomfort or a burning feeling when passing urine or during sex. In men, symptoms are less common but can include a thin discharge from the penis, pain or burning when urinating or after ejaculation, needing to pass urine more often, and irritation or soreness at the tip of the penis. Because these signs overlap closely with other infections such as thrush, bacterial vaginosis, chlamydia and gonorrhoea, they are not specific enough to diagnose trichomoniasis by symptoms alone, and a test is needed to confirm what is actually causing them.
How it is diagnosed
Trichomoniasis is diagnosed by taking a swab or, in some cases, a urine sample. For women, a swab is usually taken from the vagina, and this can often be done yourself with guidance, which many people find more comfortable and less daunting than they expect. For men, a urine sample or a swab from the urethra is used. The sample is then examined to identify the parasite, sometimes under a microscope while you wait and sometimes using a more sensitive laboratory test that detects its genetic material.
Because trichomoniasis can be harder to detect in men, a laboratory-based test is often preferred to reduce the chance of a missed diagnosis. It is well worth being tested for other sexually transmitted infections at the same time, as they frequently occur together and share similar symptoms, and a single visit can cover several at once. A discreet, confidential consultation lets a clinician advise which tests are appropriate for you and arrange them without fuss, so you get a clear answer rather than guessing at the cause of any symptoms or worrying in the meantime.
How it is treated
Trichomoniasis is treated with antibiotics and clears readily with the right course. The standard treatment in the UK is Metronidazole, an antibiotic that is very effective against this particular parasite, usually taken twice a day for five to seven days. A targeted course is sometimes supplied specifically as Metronidazole for Trichomoniasis. In some situations a single larger dose may be used instead, though the longer course is often preferred because it tends to be more reliable and is less likely to leave infection behind.
It is important to complete the full course even if you feel better partway through, and to avoid alcohol during treatment and for a day or two afterwards, because combining alcohol with metronidazole can cause an unpleasant reaction of nausea, vomiting and flushing. Mild side effects such as a metallic taste, nausea or an upset stomach are possible but usually settle. A clinician will confirm the right dose for you and check it is suitable, including during pregnancy and breastfeeding, where metronidazole can still be used with appropriate advice on the regimen. If symptoms have not settled after finishing the course, it is worth following up rather than assuming the treatment has failed.
Partners and avoiding reinfection
Trichomoniasis is easily passed between partners, so anyone you have had sex with recently should be tested and treated at the same time, even if they have no symptoms whatsoever. This is the single most important step in preventing the infection from being passed back and forth, sometimes called reinfection or the ping-pong effect, where a treated person catches it again from an untreated partner. Clinicians can advise on how far back to notify partners, and confidential partner-notification support is available if you would prefer help with that conversation.
You should avoid sex, including oral and protected sex, until you and your partner have both completed treatment and any symptoms have fully settled, which is usually around a week. If symptoms return afterwards, it may mean reinfection from an untreated partner, that the course was not completed, or occasionally that treatment needs adjusting, and a clinician can advise on the next step and whether a further test is needed. Being open with a partner, though it can feel awkward, is what protects you both and brings the episode to a clean close.
Trichomoniasis in pregnancy
Trichomoniasis in pregnancy deserves particular attention, because untreated infection has been linked to giving birth early and to babies with a lower birth weight. For this reason, treatment is generally recommended during pregnancy rather than left to clear on its own. The good news is that it can be treated safely, and a clinician will choose an appropriate regimen and dose, taking the stage of pregnancy into account and discussing any questions you have.
If you are pregnant and notice symptoms such as unusual discharge, soreness or discomfort passing urine, it is sensible to seek advice promptly rather than waiting, both for your own comfort and to reduce any risk to the pregnancy. The same principles apply as at other times: partners should be treated too, and sex avoided until treatment is complete. Testing and treatment are straightforward and confidential, and getting them sorted early is the reassuring, sensible thing to do.
Why treatment matters
Trichomoniasis is not usually dangerous, but treating it is genuinely worthwhile rather than optional. Beyond the discomfort of ongoing symptoms, in women it can cause persistent irritation and may increase the risk of acquiring or passing on other infections, including HIV, because the inflammation it causes makes the tissues more vulnerable. Left untreated, it can also simply persist and continue to be passed to partners.
The reassuring part is that these risks fall away once the infection is treated. Prompt, straightforward treatment resolves symptoms, removes the small added risk to your wider sexual health, and stops onward transmission. There is no lasting harm from a trichomoniasis infection that has been properly cleared, which is why identifying and treating it, rather than ignoring symptoms in the hope they pass, is always the better course.
Reducing your risk
Using condoms consistently and correctly for vaginal sex lowers the chance of acquiring or passing on trichomoniasis, and covering shared sex toys with a fresh condom or washing them thoroughly between uses helps too. These simple, everyday habits protect against a whole range of sexually transmitted infections, not just this one, and they are worth keeping up with any new partner. Because there is no lasting immunity after treatment, it is entirely possible to catch trichomoniasis again, so continuing these precautions matters even once a previous infection has cleared.
Regular sexual health check-ups, particularly when starting a relationship with a new partner, help pick up trichomoniasis and other infections early, often before they cause any problems and while they are simplest to treat. Testing is straightforward, discreet and nothing to feel anxious or embarrassed about; it is simply a sensible part of looking after yourself and those you are close to. If you have symptoms, a possible exposure, or would just like reassurance, a clinician can advise on a testing routine that fits your circumstances and arrange treatment where it is needed, without judgement and whenever you want it.
Frequently asked questions
Is trichomoniasis serious?
It is usually not dangerous, but it can cause discomfort and, in pregnancy, is linked to early birth, so treatment is recommended. It clears well with antibiotics.
Why can't I drink alcohol during treatment?
Metronidazole can react with alcohol to cause nausea, vomiting and flushing, so it is best avoided during the course and for a day or two afterwards.
Does my partner need treating if they have no symptoms?
Yes. Partners should be treated at the same time even without symptoms, as this prevents the infection being passed back and forth.
Can men get trichomoniasis?
Yes, although men are less likely to have symptoms. They can still carry and pass on the infection, so testing and treatment are important.
Can trichomoniasis be treated in pregnancy?
Yes. Treatment is recommended in pregnancy because untreated infection is linked to early birth, and a clinician will choose a suitable regimen for you.
Can I be treated without an in-person visit?
In many cases a clinician can assess your symptoms and history through a discreet online consultation and arrange testing and treatment where appropriate.