Bronchiolitis is the illness paediatric wards brace for every October. By January, it will have hospitalised tens of thousands of babies across the UK. It is also the illness that sends a huge number of understandably frightened parents to A&E with babies who, for the most part, can be safely managed at home.
Understanding what bronchiolitis actually does to a baby's breathing, knowing which symptoms are concerning and which are expected, and having a clear sense of when to seek help makes this a less frightening illness to navigate.
Healthbooq (healthbooq.com) provides guidance on common childhood illnesses throughout the first years of life, developed with reference to NHS and NICE clinical guidance.
What Bronchiolitis Is
Bronchiolitis is an infection of the bronchioles, the smallest airways in the lungs. The infection causes inflammation, swelling, and mucus production in these tiny tubes, which in young babies are narrow enough that even small amounts of swelling significantly affect airflow.
The vast majority of cases (around 70 to 80 per cent) are caused by RSV (respiratory syncytial virus). Other viruses, including rhinovirus, parainfluenza, and, since the pandemic, SARS-CoV-2, can cause the same clinical picture. RSV infects almost every child before the age of two. Most have a relatively mild cold. In babies under 12 months, particularly those under three months, it can progress to bronchiolitis.
The illness typically starts like any other cold: runny nose, mild cough, perhaps a low temperature. Over the next two to three days the cough becomes wetter and coarser, and breathing may become more effortful. The chest may sound wheezy or crackly. Feeds become harder because the baby is working hard to breathe and cannot coordinate sucking, swallowing, and breathing in the usual way.
The illness peaks around day three to five and then very gradually improves. The cough can persist for two to three weeks. This is normal and does not indicate the illness is getting worse.
Home Care
The cornerstone of managing bronchiolitis at home is keeping the baby adequately fed and hydrated while monitoring their breathing.
Feeds should be smaller and more frequent than usual. If a baby normally takes 150ml per feed and is struggling, offer 75ml every hour and a half rather than trying to push through full volumes. Breastfed babies may want to feed more frequently for shorter periods, which is fine. The aim is to maintain hydration, which you can check by looking at nappy output: at least four to five wet nappies per day suggests adequate hydration.
Saline nasal drops (available from pharmacies without prescription) can help loosen mucus before feeds and make it slightly easier for babies to breathe while feeding. A few drops in each nostril, used gently, can make a meaningful difference to a baby's ability to latch and feed.
Slightly elevating the head of the mattress by placing a folded towel under the mattress (never a pillow under the baby) can help with breathing in some babies.
Do not use vapour rubs containing eucalyptus or menthol in babies under three months. They can cause breathing difficulties in very young infants.
There is no antiviral treatment available for RSV bronchiolitis. Antibiotics do not help, as this is a viral illness. Bronchodilators (like salbutamol) are routinely used in adults for wheezing but have not been shown to be effective in infants with bronchiolitis and are not recommended. Paracetamol or ibuprofen can be given for comfort and temperature management, following standard dosing guidance.
Risk Groups
Most healthy term babies over three months manage bronchiolitis without hospital admission. Certain babies are at significantly higher risk of severe illness.
Babies under three months of age have the smallest airways relative to their body, the least respiratory reserve, and their immune response to RSV is more limited. They tire more quickly with the increased 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 lungs and airways and are at higher risk throughout their first winter, sometimes their second winter if they were very premature. Babies with congenital heart disease, particularly those with conditions that affect pulmonary blood flow, are at higher risk of severe hypoxia with bronchiolitis.
For eligible high-risk infants, an injection called palivizumab (Synagis) is offered monthly through the autumn and winter to provide temporary passive immunity against RSV. This is not a vaccine but a monoclonal antibody. Eligibility is assessed by the paediatric team and not all high-risk infants qualify under NHS criteria.
A new RSV vaccine (Abrysvo) is now recommended in the UK for pregnant women, typically offered between 28 and 36 weeks of pregnancy, as the antibodies cross the placenta and provide some protection to the baby in the first months of life. This is a significant development and uptake is being actively promoted.
Warning Signs Requiring Immediate Help
Call 999 or go directly to A&E if a baby shows any of the following: very fast breathing (more than 60 breaths per minute in an infant), severe recession (the skin is being sucked in between or below the ribs, at the base of the neck, or the chest is pulling in dramatically with each breath), grunting with each breath (a sign of increased effort to keep the airways open), blue or grey colour around the lips or tongue, a long pause in breathing, or the baby becomes limp and unresponsive.
Call 111 or your GP if the baby is under three months and has any signs of bronchiolitis, if the baby is not taking more than half their usual feeds, if they have had fewer than four wet nappies in 24 hours, if they seem very unwell or you are concerned, or if symptoms are getting rapidly worse over the course of a few hours.
The NHS 111 service is available 24 hours and the call handlers can assess whether the baby needs to be seen and how urgently. Do not hesitate to call if you are worried: concern is itself a valid reason to seek advice.
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.
