Oral thrush is a fungal infection in the mouth, also called oral candidiasis. It is common in healthy babies under two years old.
Babies rarely have oral thrush in their first week of life. It is most common in babies around four weeks old. Older babies can get it too, but this is less common. Some babies can have repeated infections.
Oral thrush in babies is not usually linked with other illnesses or conditions.
As well as babies, oral thrush infections most commonly affect elderly people and people who wear dentures. These infections are uncommon in other people and can be a sign of another condition or illness that has not been diagnosed.
Reproduced under the terms of Click-Use Licence number C2009000382. The content of this page has been published under a Click-Use Licence (link this to http://www.opsi.gov.uk/click-use/index) which covers the use of core Crown copyright information. The original material can be found on NHS Choices.