A yeast infection, or ‘thrush’, is an infection of the skin or mucosal membranes. These are membranes that come into contact with the air and produce mucus – like the mouth or vagina.

Yeast infections most commonly occur in a girl’s vagina but can sometimes occur on a boy’s penis as well. Yeast infections can also occur in the mouth (oral thrush) or elsewhere on the body, such as the armpit, or between folds in the skin.

Vaginal thrush – also known as Candida or candidosis is very common and affects millions of females every year. Thrush is nothing to feel embarrassed about – it’s normal to get thrush during your teens when your body is changing and developing.

What causes yeast infections and who can get them?

Yeast infections are usually caused by a fungus called Candida albicans. This fungus occurs naturally in your body – in your mouth and digestive tract, for example. It’s also found in small amounts inside a girl’s or woman’s vagina.

The amount of the Candida yeast in the body is usually kept in check but the Candida fungus can grow very quickly if the balance is disturbed. Candida yeast may start to overgrow for several reasons:

• having your menstrual period
• taking oral contraceptives (the birth control pill)
• pregnancy
• taking antibiotics or steroids
• having diabetes – especially if your blood sugar levels are not well-controlled
• having HIV/AIDs

The Candida yeast can grow quickly – it thrives in warm, dark and damp environments. Areas such as the mouth, skin folds, armpits and vagina are more vulnerable.

Candida infection of the penis can be caused by sexual intercourse with a female who has the infection. Or it can be because you have a low immunity, are taking antibiotics or have diabetes.

More than 75 per cent of women have thrush at least once at some point in their lives. However, male yeast infection is less common and the risk of getting it is only a fraction compared to females (usually thrush only affects men with a foreskin).

Anything that weakens your immune system – such as depression – may cause the overgrowth of Candida which in turn increases the chances of you developing thrush.

What are the signs and symptoms of yeast infections?

If you are female you are most likely to get thrush in your vagina. Symptoms can include:

• itching around your vagina
• redness, soreness and irritation (and/or swelling) of the labia (the skin surrounding the vagina)
• pain if you are having sexual intercourse
• burning when you urinate
• thick, white or whitish-grey discharge from the vagina (this often looks a bit like cottage cheese)

In boys and men thrush affects the penis and causes an itching or burning sensation. It can also cause red sore patches near the head of the penis or on the foreskin. Sometimes, but not usually, there is a discharge.

How are yeast infections normally diagnosed and treated?

If you have any of the above symptoms you need to see your GP. They can do some simple tests to see if it’s a yeast infection and not something else. If they think it is vaginal thrush, the GP may perform a pelvic examination. They will then take a swab of your vaginal discharge which will be analysed. The Candida yeast can be seen easily under a microscope.

The treatments for yeast infections are very effective. Usually the symptoms and infection disappear within a few days. If you have had thrush before and recognise the symptoms, you may want to go to your pharmacy and ask for something over-the-counter. This could be a vaginal cream or suppositories (special capsules inserted into the vagina). You can also take tablets orally. You usually have to treat the thrush for between three and seven days.

What’s going to help?

Oral thrush can be linked to the use of asthma medication because of the corticosteriods you inhale.  If you are using these long-term, it’s a very good idea to rinse your mouth after each dose of steroids.

Can yeast infections be prevented?

There are a few things that you can do to help prevent future yeast infections:

• Avoid wearing tight clothes or synthetic fabrics – these trap moisture close to your body and can lead to an infection.
• Take off damp/wet clothes and swimming costumes as quickly as possible.
• Avoid strongly scented feminine hygiene products.
• Try not to take too many bubble baths.
• Change tampons and sanitary towels regularly.
• Avoid using harsh soaps and shower gels.
• After using the toilet, wipe from front to back to avoid spreading yeast from the anus to the vagina.

Thrush is not a sexually transmitted infection (STI) – many people already have the Candida fungus in their bodies. The reason the fungus doesn’t normally create problems is because the immune system keeps it in check. However, in some cases, thrush can be passed on through sexual intercourse, but this is rare.

Looking forward

Yeast infections are not normally serious and don’t usually cause further problems. Some people can get chronic yeast infections, but this only usually happens if they haven’t treated previous infections properly.

For more help and information

If you would like to know more about yeast infections please ask your doctor.

Last reviewed by Great Ormond Street Hospital: 29 November 2007

Copyright © Great Ormond Street Hospital