Vaginal thrush (candidiasis): why it isn't an STI and how it's treated

Vaginal thrush (vulvovaginal candidiasis) is an infection caused by a yeast, usually Candida albicans, that lives naturally in the vagina and overgrows. It is not a sexually transmitted infection, although we include it in this section because it is linked to sexual health. It can be cured with antifungal medicine, usually within days. It is very common: according to the US CDC, around 75% of women will have at least one episode in their lifetime.

What it is and why it isn't an STI

Candida is part of the normal flora of the skin, mouth, gut and vagina. In the vagina it lives in balance with protective bacteria and causes no problems. When that balance is upset, the yeast multiplies and symptoms appear.

That is why thrush is not "caught" from someone else: it comes from your own flora. Someone who has never had sex can get it. Sex can trigger it in some people (through friction or changes in the area), and less often a partner may notice irritation on the penis. But that doesn't make it an STI, and partners don't need treatment unless they have symptoms.

What makes it more likely

• Taking antibiotics, which reduce protective bacteria.
• Pregnancy and other hormonal changes, such as some contraceptives or HRT.
• Poorly controlled diabetes.
• A weakened immune system.
• Irritated skin, warmth and moisture: tight or damp clothing, harsh soaps, douching.

Symptoms

• Intense itching and soreness around the vulva and vagina.
• Thick white discharge, often like cottage cheese, that usually doesn't smell.
• Redness and swelling of the vulva.
• Stinging when you pee or discomfort during sex.

Some people only have mild symptoms. On the penis, when it happens, it can cause redness, itching or burning on the head and under the foreskin.

Note: discharge that smells, is yellow-green or frothy points to other causes, such as bacterial vaginosis or an STI like trichomoniasis. If sex is painful, see also our article on pain during sex.

Diagnosis: when and how

There is no "window period" with thrush, because you don't catch it from a risky encounter. It is checked when there are symptoms. A clinician asks about them, looks at the area and, if needed, takes a swab of the discharge to look at under a microscope or grow in the lab.

A swab is especially useful the first time, if symptoms aren't typical, if treatment hasn't worked or if it keeps coming back. Finding Candida in someone with no symptoms doesn't need treatment: it's part of the normal flora.

If you've had a possible STI risk and have symptoms, ask for STI tests too: the symptoms can be confused.

Treatment

It's treated with antifungal medicine: a cream, a pessary or a tablet taken by mouth, depending on the case. Symptoms usually improve within a few days, and the NHS says thrush should clear within 7 to 14 days.

• If you've been diagnosed before and recognise the symptoms, a pharmacist can help. If you need treatment more than twice in six months, see a GP or nurse.
• Creams and pessaries can damage latex condoms and diaphragms, so they may not protect you. Read more in common condom mistakes.
• When can you have sex again? When you feel comfortable. If it's sore, it's best to wait until it has cleared.

When thrush keeps coming back (three or more episodes in a year), it's called recurrent thrush. It affects fewer than 5% of women and may need longer treatment over several months, as advised by your clinician.

Pregnancy

Thrush is more common in pregnancy because of hormonal changes. It isn't usually harmful, but don't self-treat: some tablets taken by mouth aren't recommended in pregnancy, and vaginal treatments are preferred. Speak to your midwife or GP. There's more in our pregnancy and postpartum guide.

Prevention

• Wash the vulva with just water or a mild, unperfumed product, and dry it well.
• Avoid douching and vaginal deodorants.
• Wear cotton underwear and avoid tight or damp clothing for long periods.
• Only take antibiotics when a clinician advises them.
• Keep diabetes well controlled, if you have it.

When to get help

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

• it's the first time you've had these symptoms;
• you're pregnant or breastfeeding;
• you're under 16 or over 60;
• treatment hasn't worked or thrush keeps coming back;
• there's a bad smell, discharge of another colour, pelvic pain, a fever or sores;
• you have a weakened immune system.

It's a very common appointment. You'll be seen without judgement, and in most cases symptoms clear within a few days.