Bronchiolitis: the chest infection in babies that needs watching closely
Bronchiolitis starts looking exactly like a cold. Then, over the next day or two, your baby's breathing changes: it gets faster, more laboured, and sometimes wheezy. For a parent watching that happen, it can feel very alarming. This article walks you through what bronchiolitis is, how it tends to unfold, how to care for your baby safely at home, and, most importantly, the specific signs that mean you need emergency help right now.
What is bronchiolitis?
Bronchiolitis is a viral infection that inflames and partially blocks the very small airways deep inside the lungs, called bronchioles. As those tiny passages swell and fill with mucus, breathing becomes harder, and babies can start to wheeze or breathe much faster than normal.
It is the most common serious respiratory infection in babies under one year old in the UK. The most frequent cause is a virus called respiratory syncytial virus (RSV), though influenza, rhinovirus and other respiratory viruses can trigger the same pattern. Bronchiolitis is not the same as bronchitis (which affects larger airways) or pneumonia (which is a bacterial infection deep in the lungs). Understanding what it is helps explain why antibiotics do not work: it is a viral infection, not a bacterial one.
Who is most at risk?
Bronchiolitis mainly affects babies under 12 months, and babies under six months are at the greatest risk of becoming seriously unwell. This is because their airways are smaller, they breathe mostly through their nose (which can block up), and they tire more easily from the extra work of breathing.
Premature babies, babies with congenital heart conditions or chronic lung disease, and those who are immunocompromised are at higher risk of needing hospital care. These babies are often offered additional protection, such as monthly injections of an RSV-preventive antibody (palivizumab) during the RSV season, through their specialist or GP.
For context: in healthy older babies and toddlers, the same RSV virus that causes bronchiolitis in young babies usually causes nothing more than a runny nose and a mild cough. This is why you might see a three-year-old in the household with just a cold while the four-month-old baby becomes much more unwell from the same virus.
How the illness develops
The first one or two days of bronchiolitis are almost indistinguishable from a common cold: runny nose, a mild cough, possibly a low fever. Your baby may feed a little less well than usual, but nothing dramatic. It is the days that follow where bronchiolitis becomes itself.
From around day two or three, the infection moves deeper into the chest. Breathing often becomes noticeably faster. You may hear a wheeze (a soft whistling sound when breathing out), and you might see your baby's nostrils flare slightly with each breath, or their chest rise and fall more visibly than normal. Feeding becomes difficult because it is hard to coordinate sucking, swallowing, and breathing when you are already working hard just to breathe.
The worst of bronchiolitis is usually around days three to five. After that, most babies slowly begin to improve, though the cough often persists for two to three weeks even after the acute phase has passed.
Caring for your baby at home
For most babies with mild to moderate bronchiolitis, careful home care is the right approach. The NHS guidance covers several practical steps.
Offer small, frequent feeds rather than your usual full-sized ones. When breathing is fast and laboured, taking a large feed is exhausting and can cause vomiting. Shorter, more frequent feeds are easier on your baby and still ensure they are getting the fluids they need. If you are breastfeeding, offer the breast more often rather than trying to get through a full feed in one go.
Saline nasal drops (available from any pharmacy without a prescription) can help clear the nose before feeds. Gently applying a few drops, waiting a moment, then using a nasal aspirator if needed can make a real difference to how easily your baby can feed.
Keep your baby upright during and after feeds where possible. A slightly upright position helps keep the airways as open as possible and reduces reflux, which is common during viral illness.
Do not give cough medicines, decongestants, or antihistamines to babies. They are not safe or effective for infants. Antibiotics will not help because bronchiolitis is a viral infection. If your baby is uncomfortable and has a fever, age-appropriate paracetamol or ibuprofen can help.
Signs that require emergency care
This is the section to read carefully, and to come back to if you are worried. Go to A&E or call 999 immediately if your baby shows any of the following:
- Breathing rate that is consistently over 60 breaths per minute (count over 30 seconds and double it)
- The skin between the ribs, below the ribs, or at the base of the throat pulls in visibly with each breath (these are called retractions, and they mean your baby is working very hard to breathe)
- Nostrils flaring wide with every breath
- Lips, tongue, or skin around the mouth looks blue or grey
- Your baby is feeding less than half of their usual amount over a 24-hour period
- Your baby seems very drowsy, unusually difficult to rouse, or does not respond normally to you
- Your baby has had no wet nappy for six hours or more
If you are unsure whether what you are seeing counts, trust your instinct and call 999 or 111. You are not wasting anyone's time. These signs exist precisely to help you know when to act.
What happens in hospital?
If your baby is admitted to hospital with bronchiolitis, the main treatments are simple but effective. If their oxygen levels are low, they will receive oxygen through a small tube near their nose or through a mask. If they are not feeding enough by mouth due to the effort of breathing, a nasogastric tube (a thin tube passed through the nose into the stomach) can be used to give milk feeds directly, so your baby does not have to work to swallow.
There are currently no antiviral medicines available to treat RSV bronchiolitis. Antibiotics will not be given unless a bacterial infection has developed alongside the viral one, which is uncommon. The focus of hospital care is on keeping your baby safe, oxygenated and hydrated while their immune system does the work of clearing the virus. Most babies admitted to hospital with bronchiolitis improve significantly within a few days.
How long does it last?
The full course of bronchiolitis is usually 10 to 14 days. The acute phase, when breathing is most difficult and feeding is hardest, typically lasts from around day three to day seven. After that, most babies gradually improve each day.
The cough often continues for two to three weeks after the worst of the illness, which can be worrying if you do not expect it. A lingering cough after bronchiolitis is very common and does not mean your baby is still seriously ill. As long as their breathing is comfortable, they are feeding well, and they are having wet nappies, the cough on its own is not a reason to seek urgent help.
Frequently asked questions
How do I know if my baby has bronchiolitis?
The key signs are: a cold that has moved to the chest over two or three days, breathing that is noticeably faster than normal, a wheeze, and difficulty feeding. If your baby's breathing is clearly faster than usual and they seem to be working harder to breathe than normal, that is the moment to seek medical advice. Call 111 if you are not sure.
Is bronchiolitis the same as RSV?
Not exactly. RSV (respiratory syncytial virus) is the most common virus that causes bronchiolitis, but they are not the same thing. RSV causes bronchiolitis specifically in young babies because their smaller airways inflame more significantly in response to the infection. In older children and adults, the exact same RSV virus usually causes nothing more than a mild cold. This is why one person in the household can have a runny nose while a small baby becomes quite unwell.
When should I take my baby to hospital with bronchiolitis?
Go to A&E or call 999 if your baby is breathing very fast (more than 60 breaths per minute), has visible chest retractions where the skin pulls in around the ribs or throat with each breath, has lips or skin that look blue or grey, is feeding less than half their normal amount over a day, or is very drowsy and difficult to rouse. Any one of these signs is enough to seek emergency care without delay.
How long does bronchiolitis last?
The acute phase, when breathing is most difficult, lasts about 10 to 14 days. The cough can continue for up to three weeks after the illness peaks. This lingering cough is very common and is a normal part of recovery, not a sign that your baby is still seriously unwell. If breathing is comfortable and feeds and wet nappies are back to normal, a cough on its own does not need emergency attention.
Can I give my baby anything to help with bronchiolitis?
Saline nasal drops help clear the nose before feeds and are safe for babies of any age. Age-appropriate paracetamol or ibuprofen can reduce fever and discomfort. Offer frequent small feeds rather than full-sized ones. There are no specific medicines that treat bronchiolitis itself. Do not give cough medicines, decongestants, or antibiotics unless a doctor prescribes them specifically.
Will my baby need to go to hospital?
Most babies with bronchiolitis are cared for at home and recover well. NHS data suggests around two to three percent of babies with bronchiolitis need hospital admission. Those most likely to need hospital care are babies under three months old, premature babies, and those with underlying heart or lung conditions. If you are at all unsure how your baby is doing, call 111 and they will guide you through whether hospital assessment is needed.
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