What is thrush?

Thrush is a fungus infection of the mouth. The condition is caused by Candida, a yeastlike fungus. Even healthy people have a small amount of this fungus in their mouth most of the time. But they don’t develop thrush, because their immune system and other germs in their mouth keep the fungus from multiplying. 

Older people or those with weakened immune systems, however, are at greater risk for thrush. People with diabetes who have high blood sugar levels are also more likely to develop the condition. Taking antibiotics for an extended period of time can also lead to thrush, since the drugs kill off some of the good bacteria that help keep Candida in check. 

Babies are at increased risk for thrush because their immune systems are still developing. In fact, thrush is so common among infants, the National Institutes of Health don't consider it abnormal unless symptoms last for more than two weeks.

How do I know if my baby has thrush? 

Babies affected by thrush will have distinct white patches or velvety sores in their mouth, particularly their inner cheeks and on their tongue, according to the American Academy of Pediatrics (AAP). Unlike the white milky coating that can be seen on babies’ tongues after a feeding, the AAP points out the white patches caused by Candida cannot be washed away or wiped off easily. 

Beneath the white substance there may be inflamed or red tissue that bleeds easily. If left untreated, the sores can get larger and increase in number. 

Although thrush can be uncomfortable for babies, it is rarely serious. A baby with thrush may be reluctant to breastfeed or bottle-feed because sucking irritates the sores in her mouth. 

In addition to the patches in the mouth, babies with thrush may also have a bright red diaper rash caused by the excess yeast. 

If you suspect that your baby has thrush, you should contact your child’s health care provider. He may be able to diagnose thrush just by looking in your baby’s mouth, but a culture of the white patches can confirm whether or not Candida is the culprit.

How is thrush treated? 

Thrush is not contagious and infants with the condition may require no treatment at all, the AAP explains. The condition often clears up on its own within a couple of weeks. 

If your infant has had thrush-related sores for at least two weeks or is not eating well as a result of the sores in her mouth, her doctor may prescribe an antifungal drug or other medication to treat the infection

For toddlers, eating yogurt that contains live cultures of Lactobacillus acidophilus encourages the growth of good bacteria and discourages the growth of yeast.

Is it safe to continue breastfeeding if my baby has thrush? 

Yes. Although thrush can pass back and forth between a mother and her baby, stopping breastfeeding will not clear up the infection once it has developed, the AAP says. For this reason, however, it is important for breastfeeding mothers and infants with thrush to be treated at the same time. 

Breastfeeding mothers will know if Candida is present because their nipples may become inflamed or red, shiny, oozy, or crusty. Nursing mothers may also feel a burning or itching sensation in their nipples during or after nursing.

Mothers who are breastfeeding an infant with thrush must take extra precautions to prevent future infections. But even babies who are bottle-fed can develop thrush. The AAP says there are a number of steps mothers can take to prevent this type of infection, including: 

  • Keep your nipples clean and dry. 
  • Change your nursing pads when they become damp. 
  • Wash your hands well and often with warm, soapy water. 
  • Throw out all bottle nipples and buy new ones. 
  • Sterilize or discard any pacifiers. 
  • Sterilize or discard teething rings and other teething toys.

Is it safe to store breast milk for later use? 

Studies show that freezing deactivates yeast, but doesn’t kill it. Since milk expressed during a thrush outbreak could be a source of infection, some sources recommend that mothers being treated for thrush not freeze milk for later use. While other sources note that human milk contains ingredients (lactoferrin and immunoglobulins) that inhibit the growth of yeast. Moreover, human milk supports the growth of lactobacillus, “good bacteria” that limit the growth of yeast. 

Milk containing yeast is unlikely to be a problem for healthy babies. Mothers concerned about safety can either not freeze milk expressed during a thrush outbreak, or heat treat (scald or boil) thawed milk expressed during a thrush outbreak.

Last updated June 9, 2020

Suggested Reads