Oral Thrush in Babies: Signs, Treatment, and Preventing Reinfection

Oral thrush is a fungal infection caused by Candida albicans — a type of yeast that normally lives in the gut and on the skin in small numbers. In newborns, whose immune systems are still maturing, the balance can tip and thrush establishes in the mouth. It's uncomfortable but not dangerous, and it responds well to treatment — as long as the treatment is thorough.

What It Looks Like

The key question parents ask is how to tell thrush from milk residue, because they can look similar.

Oral Thrush vs Milk Residue

Milk residue:

• White coating on the tongue and sometimes inner cheeks
• Easily wiped away with a clean damp cloth or finger
• Appears after a feed, less obvious before feeding

Oral thrush:

• White patches on the tongue, inner cheeks, the roof of the mouth, gums, and/or inner lips
• Patchy or speckled, sometimes described as looking like cottage cheese
• Cannot be easily wiped away — if you try, the patches are difficult to remove and the underlying skin may look red or bleed slightly
• Present even before a feed

The inability to wipe it away is the most reliable distinguishing feature. If you're not sure, ask your GP or health visitor to take a look — they can usually identify it clinically without any tests.

Other signs your baby has oral thrush:

• Reluctance to feed or fussiness during feeding (the mouth may be sore)
• Clicking sound during breastfeeding (which can also suggest tongue tie — the two can coexist)
• You may simultaneously have sore, pink, shiny nipples (nipple thrush) if you're breastfeeding

How Babies Get Thrush

Candida is a normal part of the human microbiome. Newborns encounter it during birth (from the vaginal canal), from skin contact, and from the environment. In most cases the immune system keeps it in check; in some babies — particularly those who've had antibiotics, were premature, or simply have the right local conditions — it proliferates.

Breastfeeding creates a warm, moist environment that candida finds hospitable, which is why thrush is more common in breastfed babies (though formula-fed babies can also develop it). The baby passes thrush to the mother's nipples and the mother re-passes it to the baby in a cycle that can persist indefinitely without proper treatment.

Treatment

For the Baby

The first-line treatment in the UK is nystatin oral drops (brand name Nystan). Nystatin is an antifungal that works topically — it coats the mouth and kills the candida on contact.

How to use nystatin drops:

• Shake the bottle well before each use
• Using the dropper, place the drops inside the cheek — half the dose on each side
• Give after feeds so the drops aren't immediately washed away by milk
• Gently swab any white patches with the drops using a cotton bud if advised
• Continue for the full prescribed course — usually 7 days, even if patches clear sooner

Nystatin is available on prescription from your GP. It's safe for newborns and breastfeeding mothers.

For the Breastfeeding Mother

If you're breastfeeding and your baby has oral thrush, you almost certainly need treatment too — even if your nipples don't look or feel obviously affected. Untreated nipple thrush is the most common cause of thrush recurring in the baby.

Treatment for nipple thrush:

• Topical miconazole cream (Daktarin is a commonly available brand) applied to the nipples after every feed and wiped off gently before the next
• Some GPs also prescribe oral fluconazole if nipple thrush is significant — this is safe during breastfeeding

It's important that both baby and mother are treated simultaneously. Starting the baby's treatment and not treating yourself — or vice versa — is almost certain to result in reinfection.

Sterilisation and Hygiene

During treatment, extra attention to hygiene reduces the risk of reinfection:

• Sterilise everything that goes in the baby's mouth: dummies, bottle teats, breast pump parts that contact milk. Do this after every use during the treatment period, not just daily
• Wash bras and breast pads at 60 degrees — candida survives lower temperatures
• Change breast pads frequently — moist breast pads are ideal for candida
• Wash hands thoroughly after nappy changes (candida can live in the gut and be passed via nappies)
• Don't share towels during the treatment period

When to See Your GP

See your GP if:

• You're not sure whether what you're seeing is thrush or something else
• Your baby is refusing to feed because of mouth discomfort
• Symptoms don't improve after completing the course of nystatin
• Thrush keeps coming back after treatment — this may indicate the treatment approach needs adjusting or there is an underlying factor
• You're breastfeeding and experiencing burning nipple pain, which may indicate nipple thrush alongside the oral thrush

How Long Does It Take to Clear?

Most cases of oral thrush clear within 7–14 days with proper treatment. If both mother and baby are treated simultaneously and the full course is completed, recurrence is less likely.

Occasionally thrush is more persistent — if it returns repeatedly, ask your GP about longer treatment courses or a review of hygiene practices.

A Note on Nappy Thrush

If your baby has oral thrush, they may also develop thrush in the nappy area (candida nappy rash). This appears as a bright red, inflamed rash with satellite spots — smaller red spots around the main rash. It's treated with an antifungal cream applied to the nappy area. Mentioning any nappy rash to your GP at the same time allows them to treat both sites if needed.