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.
However, if the level of fungus increases too much (called overgrowth), membranes (mucosa) in your baby's mouth can become infected.
Immature immune system
Oral thrush may occur in babies because their immune systems take time to mature, making them less able to resist infection.
Oral thrush is more common in premature babies (babies born before 37 weeks of pregnancy) because:
- their immune systems are not as strong
- they have not had as many of their mother's antibodies passed to them
Antibiotics
Oral thrush infections can also happen after treatment with antibiotics. This is because antibiotics reduce the levels of healthy bacteria in your baby's mouth, which allows fungus levels to increase.
If you are breastfeeding and have been taking antibiotics for an infection, your own levels of healthy bacteria can be affected, making you or your baby more prone to a thrush infection.
In babies, oral thrush is not usually due to poor hygiene.
