Thrush or STI: how to know the difference

Thrush is a yeast infection caused by a fungus called candida. It isn’t classed as an STI. STIs are infections caused by bacteria, viruses or parasites that are mainly passed on through sex.

Thrush and STIs can cause similar symptoms, such as itching, soreness, discharge and pain when you pee. But there are some clues:

• Thrush usually causes a thick white discharge, like cottage cheese, that doesn’t usually smell, along with itching and soreness.
• A discharge that smells fishy, is green or yellow, or looks frothy is more likely to be BV or an STI such as Trichomonas.
• Bleeding after sex or between periods, pain in your lower tummy, and blisters or sores aren’t usual signs of thrush.

Many STIs, including Chlamydia, often cause no symptoms at all, so you can have one without knowing. If you’ve had sex without a condom with a new partner, getting tested is the only way to be sure.

Thrush is a very common yeast infection that affects both men and women. About 3 in 4 women get vaginal thrush at least once in their life, and around 6 in 100 get it again and again.

Thrush is caused by a fungus called candida, which is normally harmless. You’re more likely to get thrush if you:

• are taking antibiotics
• are pregnant
• are having hormone replacement therapy (HRT)
• have diabetes that isn’t well controlled
• have a weakened immune system, for example because of HIV or chemotherapy
• have irritated or damaged skin, or use products that irritate it, such as perfumed soaps, bubble baths or vaginal washes

Thrush isn’t an STI, but sex can sometimes trigger it and, less often, pass it on. Partners don’t need treatment unless they have symptoms.

This table shows the main differences between thrush and STIs.

Mike Asher, Co-Founder at Better2Know, explains:

“Telling the difference between a thrush infection and an STI is difficult for some people. Some of the symptoms are the same and with STIs there are frequently no symptoms at all. But in women, the symptoms will usually be due to irritation in the vagina or vulva, whereas many STIs like Chlamydia will produce symptoms ‘further inside’, with symptoms being deeper as it is the cervix that gets infected. If you have had any kind of sexual encounter which you think might have put you at risk, then book an STI screen to make sure you don’t have an infection. If your test is negative you will feel happy and relieved, and if it’s positive, you can get treated. However, if you have symptoms and your tests are negative, please make sure you speak to your doctor to find out alternative causes.”

Some STIs cause symptoms that can be mistaken for thrush.

Chlamydia

Chlamydia often causes no symptoms. When it does, it can cause unusual vaginal discharge, pain when you pee, bleeding after sex or between periods, and pain in your lower tummy. In men, it can cause a white, cloudy or watery discharge from the penis and pain or swelling in the testicles.

Gonorrhoea

Gonorrhoea can cause a yellow or green discharge and a burning pain when you pee. Many women have no symptoms at all. In men, it can cause a discharge from the penis and sore testicles.

Trichomonas

Trichomonas can cause a yellow or green discharge that may be frothy or smell fishy, along with itching, soreness, and pain when you pee or have sex. Many people have no symptoms.

Genital Herpes

Genital Herpes can start with tingling, burning or itching, followed by small blisters that burst to leave painful red sores. Thrush doesn’t usually cause blisters or sores, so if you have them, get checked. Read more in “Is it Herpes or thrush?”

Bacterial vaginosis (BV)

BV isn’t an STI either, but it is often confused with thrush. It happens when the normal balance of bacteria in the vagina changes, with an overgrowth of bacteria such as Gardnerella, and sex can trigger it or pass it on. BV usually causes a thin grey or white discharge with a strong fishy smell, especially after sex, rather than itching or soreness. Half of women with BV have no symptoms, and BV can raise your risk of catching an STI. If you’re pregnant and think you have BV, see a doctor. Read more in “I got Bacterial Vaginosis after I had sex. Is it an STI?”

Thrush is treated with antifungal medicine. This can be a tablet you swallow, a tablet you put into your vagina (a pessary), or a cream to ease the irritation. If you’ve had thrush diagnosed before and you recognise the symptoms, you can buy treatment from a pharmacy. If you’re pregnant, speak to a doctor first, as thrush tablets you swallow aren’t usually used in pregnancy. Don’t use antifungal medicine more than twice in 6 months without speaking to a pharmacist or doctor.

Thrush should clear up within 7 to 14 days of starting treatment. If it keeps coming back, more than 4 times in 12 months, you may need treatment for longer, up to 6 months.

Thrush creams and pessaries can damage latex condoms and diaphragms, so condoms and diaphragms may not work as well until at least 5 days after you finish treatment.

See a doctor if:

• it’s the first time you’ve had symptoms of thrush
• you’re under 16 or over 60
• you’re pregnant or breastfeeding
• treatment hasn’t worked, or thrush keeps coming back
• you have a weakened immune system, for example because of diabetes, HIV or chemotherapy
• your symptoms don’t fit thrush, for example a strong smell, a green or yellow discharge, sores, bleeding, or pain in your lower tummy

Get urgent medical care if you have severe or sudden pain in your lower tummy, a very high temperature, or you feel faint or very unwell.

If you’ve had sex without a condom with a new partner, get tested for STIs too, even if you think it’s thrush. Having thrush doesn’t rule out an STI.

Preventing thrush

You can lower your chances of getting thrush if you:

• wash the area with water and an emollient instead of soap, and dry it properly afterwards
• wear cotton underwear, and avoid tight underwear or tights
• avoid perfumed soaps, shower gels, bubble baths, douches and vaginal deodorants
• avoid sex until thrush has cleared up if sex is uncomfortable

Preventing STIs

Use a condom for vaginal, anal and oral sex, and a dental dam for oral sex on a vagina or anus. If you have new or casual partners, get tested regularly, even if you feel fine. Read more in “Why am I itchy after sex?”

A doctor can usually diagnose thrush from your symptoms, and may take a swab from your vagina or penis. Testing for STIs is the only way to rule them out.

Better2Know offers:

• Comfort Screen: a urine test for anyone with discomfort or unusual discharge. It tests for Chlamydia, Gonorrhoea, Trichomonas, Gardnerella, Herpes 1, Herpes 2, Mycoplasma and Ureaplasma, from 14 days after sex, with results in 2 days (3 days for the home test). You can book it at one of our clinics or order a Comfort Screen home test.
• Platinum Screen: our most comprehensive STI screen. It tests for 12 infections: all of the infections above, plus HIV, Syphilis, Hepatitis B and Hepatitis C, from 28 days after sex, with results in 3 days.
• Blemish Screen: if you have a sore, blister or lump on or around your genitals, it tests a swab for Herpes 1, Herpes 2, HPV and Syphilis.

These screens don’t include a test for thrush. Not sure which test you need? Our Patient Care Team is available 24/7 on 020 7099 0955.

Can thrush be passed on through sex?

Thrush isn’t classed as an STI, but sex can sometimes trigger it or, less often, pass it on. Your partner doesn’t need treatment unless they have symptoms.

Can men get thrush?

Yes. Thrush in men usually affects the head of the penis and under the foreskin. It can cause irritation, burning, redness, a white discharge, an unpleasant smell and difficulty pulling back the foreskin. Thrush is one cause of balanitis, a sore, swollen head of the penis, which can also be caused by STIs such as Gonorrhoea or Chlamydia. Read more in “What does a male yeast infection look like?”

Can you have thrush and an STI at the same time?

Yes. Having thrush doesn’t protect you from STIs. If you might have been exposed to an STI, get tested even if your symptoms seem like thrush.

Thrush is common and isn’t an STI, but its symptoms can look a lot like some STIs. A thick white discharge with itching usually points to thrush, while a strong or fishy smell, a change in colour, sores or bleeding point to something else.

If you’re not sure, or you’ve had sex without a condom with a new partner, get tested. Book a Comfort Screen at a clinic near you or order a home test kit. Our Patient Care Team is available 24/7 on 020 7099 0955.

Not in the UK? Choose your country from the selector at the top of the page for local tests and prices.

This article originally appeared on 18 September 2020 and was last updated on 29 September 2026.

Medical review. This article was medically reviewed by Dr Steve Chapman, Doctor with a wealth of clinical experience in the field of STIs, on 2 October 2025. It is general information and not a substitute for personal medical advice.

Sources

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