Bronchiolitis is the illness paediatric wards brace for every October. By January it will have hospitalised tens of thousands of babies in the UK. It is also the illness that fills A&E waiting rooms with frightened parents whose babies, in the great majority of cases, can be safely cared for at home.
Once you understand what bronchiolitis actually does to a baby's breathing — which symptoms are part of the normal course, and which mean it's time to get help — it becomes a much less frightening illness to look after.
Healthbooq (healthbooq.com) provides guidance on common childhood illnesses through the early years, drawing on NHS and NICE clinical guidance.
What Bronchiolitis Is
Bronchiolitis is an infection of the bronchioles — the tiniest airways deep in the lungs. The virus inflames them, swells the lining, and fills them with mucus. In a baby's lung those airways are already narrow; even modest swelling chokes airflow.
Around 70 to 80 per cent of cases are RSV (respiratory syncytial virus). Other viruses — rhinovirus, parainfluenza, and since 2020, SARS-CoV-2 — produce the same picture. RSV infects almost every child by age two; most have a routine cold. In babies under 12 months, and especially those under three months, it can tip into bronchiolitis.
The illness usually starts as an unremarkable cold: runny nose, mild cough, maybe a low-grade temperature. Over the next two to three days the cough deepens and gets wetter, and breathing visibly takes more work. The chest may sound wheezy or crackly. Feeds become harder because a baby working to breathe can't easily coordinate sucking, swallowing, and breathing.
Things peak around day three to five and then very slowly improve. The cough often hangs on for two to three weeks afterwards. That is normal recovery, not deterioration.
Home Care
The job at home is straightforward: keep the baby fed and hydrated, and keep watching their breathing.
Feeds. Smaller, more often. If your baby usually takes 150ml and is struggling, try 75ml every 90 minutes. Breastfed babies often want shorter, more frequent feeds — that's fine. The benchmark for adequate hydration is at least four to five wet nappies in 24 hours.
Saline nasal drops (any pharmacy, no prescription) loosen mucus enough to make latching easier. A few drops in each nostril before a feed can be the difference between a refused bottle and a finished one.
Position. Slightly elevating the head of the cot mattress — by sliding a folded towel underneath the mattress, never a pillow under the baby — can ease breathing for some babies.
Avoid vapour rubs with eucalyptus or menthol in babies under three months. They can actually worsen breathing in young infants.
There is no antiviral for RSV. Antibiotics don't help — this is a virus. Salbutamol and other bronchodilators are routine in adult wheezing but have not been shown to help infants with bronchiolitis and aren't recommended. Paracetamol or ibuprofen are fine for comfort and fever using standard weight-based dosing.
Risk Groups
Most healthy term babies over three months ride this out at home. Some babies are at meaningfully higher risk of severe illness.
Babies under three months have the smallest airways relative to body size, the least respiratory reserve, and a more limited immune response to RSV. They tire faster from the work of breathing. Any baby under three months with bronchiolitis should be assessed by a clinician rather than managed entirely at home.
Premature babies have underdeveloped airways and are vulnerable through their first winter, sometimes their second if they were very preterm. Babies with congenital heart disease, particularly conditions affecting pulmonary blood flow, are at higher risk of dangerous hypoxia.
For eligible high-risk infants, palivizumab (Synagis) is offered as monthly injections through autumn and winter. It is a monoclonal antibody — passive immunity — not a vaccine. Eligibility is set by the paediatric team and not all high-risk infants qualify under NHS criteria.
The new RSV vaccine Abrysvo is now offered to pregnant women in the UK, typically between 28 and 36 weeks. Maternal antibodies cross the placenta and protect the baby through the first months. Uptake is being actively promoted because the protection is genuine and significant.
Warning Signs Requiring Immediate Help
Call 999 or go straight to A&E if your baby has any of:
- Very fast breathing (more than 60 breaths per minute in an infant)
- Severe recession — skin sucking in between or below the ribs, at the base of the neck, or the chest pulling in dramatically with each breath
- Grunting on each exhale (a sign they are working hard to keep airways open)
- Blue or grey colour around the lips or tongue
- Pauses in breathing
- Becoming limp or unresponsive
Call 111 or your GP if:
- The baby is under three months with any signs of bronchiolitis
- They are taking less than half their usual feeds
- Fewer than four wet nappies in 24 hours
- They seem very unwell or you are worried
- Symptoms are visibly worsening over the course of a few hours
NHS 111 is available 24/7 and the call handlers will tell you whether and how urgently the baby needs to be seen. Worry is itself a valid reason to call. You will not be wasting anyone's time.
Key Takeaways
Bronchiolitis is a viral infection of the small airways in the lungs, most commonly caused by respiratory syncytial virus (RSV), and it is the most common reason for infant hospital admission in the UK during winter. Most babies can be managed at home with small, frequent feeds and careful monitoring, but breathing difficulties and feeding refusal require urgent assessment. Babies under three months, those born prematurely, and those with underlying heart or lung conditions are at higher risk of severe illness. There is no specific antiviral treatment and antibiotics have no role; management is supportive.
