Is that little patch of white around baby's mouth leftover milk, or something more? One possible culprit is thrush, an infection in and around the mouth caused by an overgrowth of the Candida fungus (aka yeast). Though it can happen to anyone, thrush is especially common in newborns and usually appears in infants under six months of age.
It's normal to have some Candida in the mouth and digestive systems—it indicates a healthy immune system. But the fungus can overgrow and infection can set in when the immune system is weakened or not fully developed, as is the case with infants.
Taking steroids or antibiotics can put you or your baby at a higher risk, since the medicines strip the "good" bacteria that keeps the yeast in check, says Dr. Preeti Parikh, a board-certified pediatrician, assistant clinical professor in the Pediatrics Department at the Mount Sinai School of Medicine, and an American Academy of Pediatrics fellow and spokesperson.
Though there's no evidence that breastfeeding your little one increases her chances of getting thrush, it's not unusual for the infection to be passed between Baby and mom during nursing sessions, says Dr. Parikh. (Candida passes easily through cracked nipples, a common issue for breastfeeding mamas.)
The tell-tale signs of yeast overgrowth are painful white patches on your baby's tongue, lips, gums, inner cheeks, and roof of the mouth that do not wipe off with a wet washcloth. The infection can also spread to the esophagus, making swallowing especially painful for her.
Thrush presents differently in breastfeeding moms. Your nipples may be red, flaky, crusty, itchy or burning, and you may also feel an intense stabbing or burning pain in one or both breasts during or shortly after feedings. "This can indicate a fungal infection within the milk ducts," Dr. Parikh says.
For some babies, thrush is no big deal. But for others, the excess yeast can lead to a sore mouth, and your baby may shun feedings because it's too painful. Though thrush is usually a mild condition, it can also affect the skin, mucus membranes, and the diaper region, so keep an eye out for diaper rashes.
In some cases, your baby's thrush can go away on its own, and your pediatrician may not prescribe medications. But if he's symptomatic or appears to be uncomfortable, your ped may prescribe an antifungal liquid, which you'd apply to the patches four times a day for at least a week, Dr. Parikh says. "For mom who is breastfeeding, an antifungal ointment should be applied to the nipples after nursing."
You'll also need to take extra care when cleaning pacis and bottles: "Make sure to wash the nipples and bottles in hot water or in the dishwasher after each use, because if they're not clean, that can also cause thrush and/or can reinfect baby with the fungal infection," Dr. Parikh says.