If your infant is extra fussy during feedings and you notice white patches in her mouth, she may have an oral yeast infection known as thrush.

But what exactly is thrush, and how can you help your baby feel better? Here's the deal.

What is thrush in babies?

Both common and not usually serious, thrush is a type of yeast infection that typically appears as white or yellow irregularly shaped patches or sores that coat your baby's mouth. Thrush often appears on the gums, tongue, roof of the mouth and/or insides of the cheeks.

Thrush in babies is often caused by a yeast or fungus called Candida albicans. While it's just a mild infection, thrush can be uncomfortable or even painful for your baby — and for you if you're breastfeeding and your little one passes the infection to you.

How do babies get thrush?

Though the fungal infection known as thrush shows up in your baby's mouth, it probably started in your birth canal as a yeast infection, and that's where your baby picked it up as she made her way into the world.[1]

Candida is an organism that normally hangs out in the mouth, throat, gut or vagina and is typically kept in check by other microorganisms. But if you get sick, start using antibiotics or experience hormonal changes (like those during pregnancy), the balance can be upset, allowing the Candida to grow and cause the infection.

Since thrush is usually picked up at birth, it's most common in newborns and babies under 2 months. Older babies can also develop thrush if they've been taking antibiotics to fight another infection (which kills off the good bacteria that keep yeast in check) or have a depressed immune system.[2]

Thrush can also develop if a breast is not properly dried after feeding and yeast grows, causing an infection. Pacifiers or bottles can cause a reinfection if they're not cleaned properly.

Baby thrush symptoms

Here are a couple of common signs of thrush in babies:

White patches inside your baby's mouth

A white coating or patches of white on the tongue, gums, inside cheeks or roof of the mouth can be a sign of thrush — or they can simply be caused by milk residue, which often stays on a baby's tongue after feeding but usually dissolves within an hour. 

To tell whether or not your baby's white tongue is caused by milk or this kind of fungal infection, try to wipe it off gently using a soft, damp cloth or a gauze-covered finger. If the tongue is pink and healthy-looking after wiping, no further treatment is necessary. If the white patch doesn't come off very easily, or it does and you find a raw, red patch underneath, it's likely thrush, and you should contact the pediatrician.

Fussiness during feeding 

If your baby starts to suck at mealtime or on a pacifier, but then turns away in pain, that's another sign of thrush.

Is thrush contagious?

If you're breastfeeding, then chances are your baby isn't the only one that yucky yeast is affecting. Yeast infections are passed back and forth from a baby's mouth to a mother's breast during nursing sessions (and then back and forth again if both members of the breastfeeding team aren't treated).

Symptoms of nipple thrush include burning and sore nipples, along with a pink, shiny, itchy, flaky and/or crusty appearance. There may also be sharp shooting pains in the breast during or after feeds.

Sometimes if your baby has thrush, she can also wind up with a yeast infection diaper rash (also referred to as yeast diaper rash), which is an angry, red rash on her bottom caused by a yeast infection.

Baby thrush treatments

Since thrush is easily passed back and forth, it's best if both you and your baby get treated.

For your baby, your pediatrician may prescribe an antifungal medication (such as Nystatin), which is applied topically to the insides of the mouth and tongue multiple times a day for 10 days. 

Be sure to get it on all the white patches in your baby's mouth if that's the remedy your doctor has given you. In a tough case, fluconazole (brand name Diflucan), an oral medication administered via dropper, may be prescribed.

Babies with thrush who also develop yeast infection diaper rash can be treated with a different prescription antifungal medication specifically for that area.

If you have nipple thrush, your doctor will likely recommend that you apply a prescription antifungal cream to your breasts.

With medication, the infection should take a week or so to clear up. Check in with your doctor if it doesn't.

Can you prevent thrush in babies?

There's nothing you can do to prevent a baby from encountering yeast in the birth canal — unless you have a C-section, she's got to come through it on her way to meet you.

But you can avoid future infections by regularly cleaning and sterilizing pacifiers, bottles and breast pump parts that touch your nipples.

Also helpful: allowing your breasts to completely dry between feedings to prevent the growth of bacteria and other microbes, changing nursing pads after feedings, wearing cotton bras that don't trap moisture and washing those bras frequently in hot water (drying them in the sun may provide extra protection).

Since antibiotics can trigger a yeast infection, they should be used only when needed — and that goes for both you and baby.

Can I still breastfeed if my baby has thrush?

Breastfeeding doesn't have to be interrupted if one or both of you have been diagnosed with thrush, but the condition can make feeding painful for you — another reason why prompt treatment for both of you is needed.

One thing that can help if you're breastfeeding with thrush, provided you have the privacy and cooperative weather, is exposing your nipples to sunlight for a few minutes each day, since yeast hates sun. Probiotics may help speed recovery and keep yeast at bay too, and they're safe to take while you're breastfeeding.

Even if your baby is irritable during feedings, keep offering the breast or bottle, if you're pumping or formula-feeding. Once the treatment kicks in and her symptoms start to subside, she'll be back to eating normally again before you know it.