Oral thrush is a fungal infection in the mouth that is particularly common in babies and young children. It is usually harmless and easily treatable.

Around one in every 20 newborn babies are affected by oral thrush, rising to around one in every seven babies in the fourth week of life.

After this, the chances of your baby developing thrush will gradually decrease.

Signs and symptoms

The main symptom of oral thrush is a white coating on your baby’s tongue, although there may also be white patches elsewhere in the mouth. This coating may look like curd or cottage cheese and usually cannot be rubbed off easily.

If your baby has a white coating on their tongue that does rub off easily, it is more likely to be milk coating the tongue and not thrush.

Babies may not seem bothered by the patches, but they may be reluctant to feed – or keep detaching from the breast during feeds – if they are sore.

There may also be associated nappy rash caused by the same infection that needs to be treated as well.

When to seek medical advice

Oral thrush in babies isn't usually serious, but you should visit your GP if you think your child may have the condition. You can also ask your health visitor for advice or call NHS 111.

If there is any doubt about the diagnosis, your GP may take a swab from your baby's mouth and send it to a lab to be tested.

Why does my baby have oral thrush?

Oral thrush is caused by a yeast fungus called Candida albicans.

Healthy people have this fungus in their mouths and it does not normally cause problems. But it can overgrow and infect the membranes in the mouth.

Babies are at an increased risk of oral thrush because their immune systems have not yet fully developed and are less able to resist infection. This is particularly the case with babies born prematurely (before 37 weeks of pregnancy).

Oral thrush can also affect babies if they have recently been treated with antibiotics because antibiotics reduce the levels of healthy bacteria in your baby's mouth, which can allow fungus levels to increase.

If you are breastfeeding and have been taking antibiotics for an infection, your own levels of healthy bacteria in your body can be affected, which can also make you prone to a thrush infection that may then be passed to your baby during breastfeeding.

Treating oral thrush in babies

If your GP or health visitor feels your baby needs treatment, they will probably prescribe an antifungal medicine. The two main antifungal medicines used to treat oral thrush in babies are miconazole and nystatin.

These medications usually need to be used up to four times a day and are most effective if used after your baby has had a feed or drink.

Continue to use the medicine for two days after the infection has cleared up as this will help prevent the infection coming back. If treatment hasn't fully cleared the thrush after a week of treatment, speak to your GP or health visitor again for advice.

Miconazole

In most cases, miconazole will be the first treatment recommended by a GP. It is available as a gel that you apply to the affected areas using a clean finger. It's important only to apply a little at a time and to try to avoid the back of your baby’s mouth to reduce the risk of choking.

A small number of babies are sick after being treated with miconazole, but this side effect usually passes and is not normally any cause for concern.

Nystatin

In some cases, your GP or health visitor may recommend an alternative medication called nystatin. This comes as a liquid medicine (suspension) that is applied directly to the affected area using a dropper (oral dispenser) supplied with the medicine.

Nystatin does not usually cause any side effects and most babies will have no trouble taking the medication.

Advice for breastfeeding mothers

If your baby has oral thrush and you're breastfeeding, it's possible for your baby to pass a thrush infection to you. This can affect your nipples or breasts and cause nipple thrush.

Symptoms of nipple thrush can include:

• pain while you're feeding your baby, which may continue after the feed is finished
• cracked, flaky or sensitive nipples and areolas (the darker area around your nipple)
• changes in the colour of your nipples or areolas

If you have thrush in your nipples, or there is a risk of your baby passing thrush on to you, you will normally be advised to continue breastfeeding while using an antifungal cream such as miconazole to treat the infection. You should apply the cream to your nipples after every feed, and remove any that's left before the next feed.

In severe cases of nipple thrush, antifungal tablets may be recommended.

Can oral thrush be prevented?

It's not clear whether it is possible to prevent oral thrush in babies. Some doctors suggest the following advice may help:

• sterilise dummies regularly, as well as any toys that your baby puts in their mouth
• sterilise bottles and other feeding equipment regularly, especially the teats

Washing your hands thoroughly after changing your baby's nappy can also be helpful in stopping thrush spreading because the infection can be passed through their digestive system.