What is oral thrush?

Thrush is an infection caused by a yeast germ called Candida spp. The mouth is a common site where Candida spp. causes infection. Candidal infection in the mouth is called oral thrush. Other common sites for thrush to develop are the vagina, nappy area, and nail folds. (See separate leaflets called 'Vaginal Thrush', 'Candidal Skin Infection' and 'Nappy Rash' for more details about other types of thrush.)
Why do some babies get oral thrush?

Small numbers of Candida spp. commonly live on healthy skin and in a healthy mouth. They are usually harmless. However, an overgrowth of Candida spp. can occur in the mouth of some babies. This can cause a bout of oral thrush.

This overgrowth may happen because the baby's immune system is still quite immature and so cannot control the Candida spp. levels. Another possible cause for oral thrush infection is if your baby has had a recent course of antibiotics. This is because the antibiotics can kill off healthy bacteria that live in your baby's mouth. These healthy bacteria normally help to control the levels of Candida spp. in your baby's mouth. If there are less healthy bacteria around, candidal overgrowth can occur. Also, if you are breast-feeding and you have recently been on antibiotics yourself, the levels of your healthy bacteria can be affected. This can make you, or your baby, more likely to develop thrush.

About 1 in 7 babies develops a bout of oral thrush at some point. It is most common in babies younger than 10 weeks, but it can occur in some older babies too. Oral thrush is not usually due to poor hygiene, and it does not usually mean that your baby is ill in any other way. Some babies have recurring bouts of oral thrush.
What are the symptoms of oral thrush?

White spots usually develop in your baby's mouth and on their tongue. The spots may join together to form larger spots called plaques. They may become yellow or grey. Your baby may not be bothered by the infection. However, sometimes their mouth becomes sore. Some babies may drool saliva, or refuse to feed properly because of soreness.

Note: if you are breast-feeding, it is possible that your baby can pass on thrush infection from their mouth to your nipples. This can be very painful for you. Your nipples can become cracked and sore. See your doctor if you think that you may have thrush infection of your nipples. Your doctor may suggest some cream to apply to your nipples to clear up the infection.
What is the treatment for oral thrush?

In some babies, no treatment is needed. Many mild cases of oral thrush only last for a short time - just a few days or so - and clear without any treatment.

If treatment is started, your doctor will usually prescribe a gel that contains an anti-thrush drug called miconazole. You smear this gel on to the affected areas in your baby's mouth, using a clean finger, as often as prescribed by your doctor. Follow the instructions carefully. Use the gel after a feed. To avoid the very small risk of choking, apply a little at a time and not to the back of the throat. The drug works by killing the candidal germs within the inside of your baby's mouth. Strictly speaking, miconazole gel is not licensed to be used in babies under four months old. However, many doctors are happy to recommend its use in babies of all ages.

An alternative treatment for oral thrush is drops which contain an anti-thrush drug called nystatin. You use a dropper which comes with the drops to place the liquid on to affected areas within your baby's mouth. Nystatin drops tend to be used if miconazole is not suitable for your baby for some reason, or if miconazole gel has not been effective.

You should continue with the treatment that your doctor prescribes, for two days after the thrush has cleared. See your doctor if the thrush has not cleared within seven days of starting treatment.
Can oral thrush be prevented?

Most bouts of oral thrush occur for no apparent reason. However, the following tips may help to prevent some bouts:
Regularly sterilise all dummies and other mouth toys used by your baby.
If you bottle-feed, regularly sterilise all feeding equipment, especially teats.
Some people suggest giving a baby a drink of sterilised water after a feed. This rinses away any residual milk in the mouth which Candida spp. may thrive on.