Most of the time, a baby who sleeps with their mouth open is simply working around a blocked nose. Babies rely on their noses to breathe, so a cold or a build-up of dried mucus quickly pushes them to breathe through their mouth, and the habit usually fades once the nose clears. If mouth breathing carries on night after night, especially with snoring, snorts, gasps or pauses, it can point to enlarged adenoids or tonsils or obstructive sleep apnoea, which a GP should check soon. Long breathing pauses, a change of colour or a struggle to breathe are emergencies at any age.
Why does my baby sleep with their mouth open?
Tresillian in Australia explains that babies breathe through their nose, so a blocked or stuffy nose makes breathing harder, and that their airways are small and narrow, so even a little mucus or swelling can make a difference. When the nose is partly blocked, the mouth takes over.
The common reasons, roughly from youngest to oldest:
| Cause | Typical age | Clues |
|---|---|---|
| Dried mucus in the nose | Newborns | Snuffly, whistling nose; otherwise well |
| A cold or other virus | Any age | Runny nose, cough, maybe a fever |
| Long-term allergy or hay fever | Varies | Ongoing blocked or runny nose |
| Enlarged adenoids or tonsils | Toddlers | Snoring most nights, nasal blockage |
| Obstructive sleep apnoea | Usually toddlers and older | Snoring with gasps, snorts or pauses |
The AAP's newborn behaviour guide says nasal noises in newborns usually come from dried mucus, and that a baby with these noises most likely doesn't have a cold. It also notes that a blocked nose can get in the way of feeding, because babies can't breathe through a closed mouth while they feed.
Plenty of parents notice their baby's mouth drops open during deep sleep, too. On its own, with quiet, easy breathing, normal colour and no snoring, that isn't one of the warning signs listed by the AAP, the NHS or the Royal Children's Hospital Melbourne.
When is sleeping with the mouth open normal?
It's usually nothing to worry about when:
- your baby has a cold or snuffly nose and the mouth breathing settles as it clears
- their breathing is quiet or only gently snuffly, without effort
- their colour stays normal
- they feed well and seem their usual self when awake
It's worth a closer look when it carries on most nights for weeks, comes with snoring, or your child seems tired, grumpy or unrested during the day. The AAP's sleep apnoea guide lists frequent snoring and problems breathing at night, plus daytime sleepiness, trouble paying attention and behaviour problems, as signs to tell your child's doctor about.
Could a blocked nose or cold be the cause?
Very often, yes. The AAP's advice on sleep with a stuffy nose says congestion makes breathing harder for babies and can keep them awake. It suggests:
- Plain saline drops (no medicine) in each nostril.
- Gentle suction with a bulb syringe or aspirator afterwards.
- Doing this before feeds and sleeps, so your baby can breathe while they suck and settle.
- A cool-mist humidifier placed out of reach, cleaned as the maker directs.
Tresillian adds that blocked noses make feeding hard work, so babies may take smaller feeds and wake sooner, and suggests plenty of fluids and cuddles. For more on easing a blocked nose, see colds and congestion and baby stuffy nose and sleep.
What are enlarged adenoids and tonsils?
Adenoids are small lumps of tissue at the back of the throat, behind the nose. The NHS says enlarged adenoids can make it hard to breathe through the nose, which can lead to mouth breathing or snoring, and can also cause sleep apnoea, glue ear and frequent ear infections. It says adenoids usually start to shrink around age 4 and disappear by early adulthood.
The Royal Children's Hospital Melbourne says tonsils and adenoids grow most quickly between the ages of 2 and 7, which is why snoring and mouth breathing from big tonsils or adenoids are more typical in toddlers and preschoolers than in young babies.
Not every child with large tonsils or adenoids needs treatment. The NHS says a doctor may suggest waiting to see whether the problems improve on their own, depending on how serious they are.
What is obstructive sleep apnoea in children?
In obstructive sleep apnoea (OSA), the muscles of the upper airway relax during sleep and the airway partly or fully closes, so breathing stops and starts. The RCH says about 15 to 20 per cent of children snore, but OSA affects only about 2 to 3 per cent. The Sydney Children's Hospitals Network gives similar figures: around 20% of children snore and around 1 to 3% have OSA.
Signs at night, from the RCH and SCHN:
- loud or frequent snoring
- pauses in breathing, often ending with a snort, gasp or grunt
- choking or gasping in sleep
- restless, sweaty sleep
- unusual sleep positions, such as propping themselves up
- breathing through the mouth instead of the nose
Signs during the day can include tiredness or headaches in the morning, daytime sleepiness, and attention, behaviour or learning problems.
The AAP says children with larger-than-normal tonsils and adenoids are at higher risk, as are children with Down syndrome, cerebral palsy, differences in the face and jaw, or who are above a healthy weight. The RCH adds long-term allergy or hay fever.
Diagnosis and treatment. The RCH says to see your GP first, who may refer your child to a paediatrician or ear, nose and throat specialist, and that overnight monitoring at home or in hospital can help diagnose OSA. The AAP calls removing the tonsils and adenoids the most common and effective treatment, but notes it isn't always successful, so follow-up matters; the RCH says it cures OSA in 80–90 per cent of children. Some children need other treatments, such as CPAP, a mask that delivers steady air pressure during sleep.
Which breathing pauses in sleep are normal?
Young babies often breathe irregularly. The AAP's newborn guide calls pauses of under 10 seconds "periodic breathing" and says they're normal if your baby seems comfortable during them. AAP pages differ on when it settles, from about 1 month in the newborn guide to about 6 months in the sleep apnoea guide.
| What you see | What to do |
|---|---|
| Pause under 10 seconds, normal colour, comfortable | Normal periodic breathing |
| Newborn pause over 10 seconds, now breathing normally | Get medical help today, straight away |
| Pause over 20 seconds | Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) now |
| Any pause with pale, blue or grey colour, or floppiness | Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) now |
| Pauses in a baby who is unwell or feverish | Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) now |
| Snoring with snorts, gasps or pauses in a well child | Talk to your GP soon |
The 10-second rule comes from the AAP's newborn guide, which says to seek care now if breathing stopped for more than 10 seconds and is now normal. For babies over about 6 months and toddlers, the 20-second rule and any colour change are what matter. The AAP's sleep apnoea guide says to call an ambulance if breathing stops for more than 20 seconds, the skin turns pale, bluish or greyish, muscle tone changes, or there's a fever or other sign of illness. Baby sleep sounds covers other normal night noises.
Is it safe to raise my baby's cot or use a pillow?
No. However blocked your baby's nose or however loudly they snore, keep them on their back, on a firm, flat mattress, with nothing else in the cot.
- The AAP says propping a baby up on towels or pillows, or tilting the mattress, is not safe, because the airway works like a straw and is easiest to breathe through when it's straight.
- NICHD Safe to Sleep says inclined or tilted sleep surfaces are not safe, and that wedges, positioners and inclined sleepers are linked to injury and death.
- The AAP's safe sleep guide says side sleeping is just as dangerous as tummy sleeping.
- Red Nose in Australia says sleeping on the back helps keep a baby's airway clear and their protective reflexes working.
Some sleep apnoea advice for older children, such as encouraging side sleeping, isn't meant for babies. Don't change your baby's sleep position on your own; ask your doctor first. See safe sleep.
What should I record for the doctor?
A short video of your child sleeping, with sound, is one of the most useful things you can bring, ideally on a night when the snoring or pauses are at their worst. Note how many nights a week it happens, roughly how long any pauses last, whether there are snorts or gasps, and how your child is during the day. Mention colds, ear infections and any allergy symptoms too.
When to get help
The NHS list of urgent signs also includes breathing very fast, a high-pitched or wheezing sound when breathing, and pausing or irregular breathing. Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) for very fast breathing, for pauses in a child who seems unwell, and for snoring that comes with a struggle to breathe or a change of colour. On brown or black skin, colour changes may be easier to see on the palms, soles, lips or tongue.
Get medical help today (same-day GP, after-hours doctor or a health advice line (Pregnancy, Birth and Baby on 1800 882 436 in Australia, NHS 111 in the UK, your pediatrician's after-hours line in the US)) if your newborn had a breathing pause of more than 10 seconds and then recovered, if a blocked nose is stopping your baby feeding or they're feeding much less than usual, or if they have fewer wet nappies.
Talk to your GP or child-health nurse soon (book now rather than waiting for the next routine check) if your child snores most nights, snorts, gasps or pauses in their sleep, sleeps restlessly with their mouth open most nights, or seems tired during the day.
