Is a yeast infection an STI?

Reviewed by our clinical team

Yeast infections like thrush cause harmless – but often uncomfortable – symptoms like itching and thick, white vaginal discharge.

Although they can occasionally be passed on during sex, yeast infections aren’t considered “sexually transmitted”. Most of the time, something like vaginal thrush is caused by an overgrowth of yeast that was already present in your system. 

What causes a yeast infection?

A yeast infection like thrush is caused by a type of yeast fungus called candida, which occurs naturally in the human body.

Normally, “good” bacteria in the body keep candida in check, preventing it from multiplying too much. However, when there’s a disruption to the natural balance of bacteria, candida begins to thrive, resulting in the unpleasant symptoms of thrush. 

Yeasts thrive in warm, moist conditions. That's why the vagina is an ideal place for them. They also like oestrogen - that's why taking the combined contraceptive, HRT or being pregnant can make you prone to thrush. Yeasts also like sugar, so having poorly controlled or newly diagnosed diabetes can also cause thrush. People who have a low immune system due to illness or medication can also get thrush.

Can a yeast infection be passed on during sex?

Yes, a yeast infection like thrush can be passed on during sex, although this is uncommon. Having lots of sex without a condom can also cause thrush. Semen is alkaline and lots of it can change the natural balance in your vagina from slightly acidic to slightly more alkaline; this can encourage yeasts to grow. Likewise, over washing can disrupt the natural balance.

This means if you’re having symptoms, or if you notice them in your partner, it’s best to avoid sex until your thrush has cleared up. Sometimes thrush goes away all on its own, but sometimes you need treatment to stop the discharge or itch.

Can men get thrush from a female partner?

Yes, it’s possible for a man to get thrush after having sex with a woman who has a yeast infection – but again, this is rare. This is because the penis isn't a great "host" for thrush, so any yeast cells usually won't take hold unless your immune system is weakened, or you have newly diagnosed or poorly controlled diabetes.

In men, thrush normally affects the head of the penis, causing redness, itching and irritation. You might Some men get a white discharge under the foreskin or an unpleasant smell.  Others may find it difficult to pull your foreskin back. 

How do I know if I have an STI or a yeast infection?

There can be a bit of overlap between the symptoms of thrush and the symptoms of a sexually transmitted infection – both can cause itching around the genitals and/or (vaginal) discharge.

However, thrush has quite a distinctive symptom: thick, lumpy, white discharge with the consistency of cottage cheese. If you’re having discharge like this, and itching, redness or swelling around the genitals, you probably have thrush. If your symptoms aren’t clear cut you might have BV (bacterial vaginosis) or  an STIs such as chlamydia, trichomonas or gonorrhoea.

Regardless, it’s always a good idea to see your GP or go to a sexual health clinic if you’re having thrush symptoms for the first time. It’s also a good idea to see a doctor or nurse if you keep getting thrush, or if treatment hasn’t worked for you. If you’ve had it before you can go straight to your pharmacist to buy thrush treatment. 

Can thrush be treated with antibiotics?

STIs like chlamydia and gonorrhoea can be treated with antibiotics, but this is not the case with yeast infections. Thrush is caused by the candida fungus and not by bacteria, which is why antibiotics aren’t a suitable treatment – instead you’ll need an antifungal medicine.

For vaginal thrush, treatment normally comes as a tablet you swallow, a tablet you insert into your vagina (known as a pessary) and/or a cream you rub onto your vagina. You should find that your symptoms clear up within seven to 14 days of starting treatment.

How about natural treatments for thrush?

If your symptoms are mild, or you are keen to avoid taking tablets or using creams, you can certainly try natural treatments. Some women find that dipping a tampon in natural (no flavour, no sugar) yoghurt and inserting this overnight helps. Natural yoghurt boosts the natural lactobacilli of the vagina and can stop the yeasts from multiplying. If your thrush is very mild it might go away all by itself. You can find out more about home remedies here. 

Should I visit a sexual health clinic for thrush?

Yes, if you want to! Thrush isn’t considered an STI, but sexual health clinics are well equipped to test for and treat conditions affecting the genitals. They also offer walk-in appointments and can sometimes get test results quicker than some GP surgeries, so you might find it more convenient. 

Get tested for STIs with Online Doctor

If you’re concerned that you might have an STI and you want to get tested, there are lots of options, including ordering a home STI test kit from Online Doctor. This service is only available to people who aren’t currently having symptoms – if you are having symptoms, you should see a doctor or nurse in person, usually at a sexual health clinic. 

References

https://patient.info/sexual-health/vaginal-discharge-female-discharge/vaginal-thrush-yeast-infection
https://www.nhs.uk/conditions/thrush-in-men-and-women/
https://www.nhsinform.scot/illnesses-and-conditions/sexual-and-reproductive/thrush/
https://www.nhs.uk/conditions/sexually-transmitted-infections-stis/
https://www.nhs.uk/live-well/sexual-health/keeping-your-vagina-clean-and-healthy/