As the days get shorter, the same three illnesses come round again: bronchiolitis in babies, viral-induced wheeze in toddlers and preschoolers, and croup in both. They are all caused by viruses, which is why the doctor won’t reach for antibiotics. They all get better on their own. What the doctor does, and what you do at home, is support your child while their body clears the bug: help them breathe if breathing is hard, and help them drink if drinking is hard. In two of the three there is also a medicine that opens or shrinks the swollen tube.
This post goes through each one: where it swells, what it sounds like, what helps and what doesn’t. If you want the short version on coughs in general, it’s in our cough guide.
Three viruses, three places
Air comes in through the nose and mouth, down one big pipe (the windpipe), then into branching tubes inside the lungs that get smaller and smaller. Each of the three illnesses swells a different level of that tree.
| Bronchiolitis | Viral-induced wheeze | Croup | |
|---|---|---|---|
| Who | Babies under 1, most often 3 to 6 months | Mostly 1 to 5, and 1 to 2 overlaps with bronchiolitis | 6 months to 6 years, peaking in the second year |
| What swells | The smallest tubes deep in the lungs | The larger breathing tubes inside the lungs | The voice box and windpipe |
| The sound | Fast, crackly or wheezy breathing | A whistle on breathing out | A seal-like bark, and a harsh rasp on breathing in |
| Medicine | None. Breathing and feeding support if needed | The blue inhaler. Oxygen if severe | One dose of steroid. Oxygen if severe |
Which one? Start with the age
The same cold virus does different things to different-sized airways, so age is the first clue.
- Under 1: bronchiolitis. UK guidance says it happens under 2 and mostly in the first year, peaking between 3 and 6 months. About one baby in three gets it in their first year, and two or three in a hundred are admitted to hospital.
- Over 2: a wheeze with a cold is more likely viral-induced wheeze. Viral wheeze and early asthma are described as unusual under 1.
- 1 to 2: the grey area. The two pictures overlap, and a doctor listens to the chest and looks at the pattern to tell them apart: a wheeze without crackles, a child who has wheezed with colds before, or eczema and hay fever in the family all point towards wheeze rather than bronchiolitis.
- Croup sits across both bands: mostly 6 months to 6 years, with the second year the most common.
The distinction matters for one reason. The blue inhaler that helps a wheezy 3-year-old does nothing for a 4-month-old with bronchiolitis, because the swelling is in tubes too small for it to open. That’s why the treatment changes with the age.
Bronchiolitis: the smallest tubes
A cold virus, usually RSV, gets into the tiniest air tubes deep in a baby’s lungs. They swell and fill with mucus, and air struggles to get through. It starts as an ordinary cold for a day or three, then the cough worsens, breathing gets faster and noisier, and feeding gets harder because a baby can’t suck and breathe fast at the same time.
How long: worst between days 3 and 5, then slowly better. The cough is gone in nine babies out of ten by 3 weeks. Feeding usually dips after day 3 to 5, which is when most babies who need hospital are admitted.
What helps: nothing that treats the virus. NICE, the UK guideline body, lists what not to give: antibiotics, salbutamol (the blue inhaler), steroids, and nebulised salt water or adrenaline. None of them has been shown to help. What a baby with bronchiolitis needs is support while it passes:
- Breathing support. At home, that’s keeping them upright when awake and clearing the nose with saline drops before feeds. In hospital, if the oxygen level in the blood drops, it’s extra oxygen through soft prongs in the nose, sometimes warm high-flow air through the same prongs, and only rarely a breathing machine or intensive care.
- Feeding support. At home, smaller feeds more often. In hospital, if a baby can’t take enough by mouth, milk through a thin tube passed down the nose into the stomach, and a drip if even that isn’t tolerated.
Babies under 3 months, babies born early (especially before 32 weeks), and children with a heart or lung condition, a muscle condition or a weakened immune system are more likely to need that help. Ask sooner for them.
Viral-induced wheeze: the larger tubes
In a toddler or preschooler, the same kind of cold virus irritates the larger breathing tubes inside the lungs. The lining swells, the thin muscle wrapped around the tubes tightens, and the space for air gets smaller. Air squeezing out through a narrowed tube whistles, and that whistle on breathing out is the wheeze. Young children get it more than older ones because their tubes are small to begin with.
How long: an episode usually lasts 2 to 4 days, tied to the cold. It can come back with the next cold, and the next, and the child is well in between. Most grow out of it: around six in ten have stopped wheezing by 6 and eight in ten by 10. It is not the same as asthma, and asthma is rarely diagnosed under 5 for exactly that reason.
What helps:
- The blue inhaler, if they’re working hard. It’s salbutamol. It relaxes the tightened muscle around the tubes, opening them up, and works within minutes. A doctor will prescribe it with a plan: how many puffs, how often, and how to step down over the next few days. Always through a spacer, with a mask for a small child: shake, one puff into the spacer, ten normal breaths, repeat. A crying child gets almost none of it, so calm first, puffs second.
- Oxygen, if it’s severe. A child whose breathing is very hard work, or whose oxygen level has dropped, is given oxygen in hospital, and occasionally more breathing support than that. Sometimes a doctor in hospital adds a short course of steroid. The evidence for steroids in this age group is mixed, so it’s the doctor’s call rather than something to expect.
- Keep them drinking. A breathless child drinks less. Small amounts, often. Fewer wet nappies or no wee for 12 hours is a reason to be seen the same day.
The escalation point is the same on every UK wheeze plan we read: if the inhaler isn’t lasting four hours, they need to be seen that day. If they’re not improving after five puffs under the age of 5, or ten puffs over 5, or are too breathless to talk, eat or drink, it’s an ambulance, with ten puffs every ten minutes until it arrives.
Croup: the windpipe
Croup is a virus, most often parainfluenza, swelling the voice box and the top of the windpipe: the one main pipe that connects the outside world to the lungs. A narrowed windpipe gives croup its two sounds. The cough turns into a bark, like a seal, and the voice goes hoarse. And when the swelling is bad enough, there’s a harsh, rasping noise on breathing in, called stridor. Wheeze is on the way out; stridor is on the way in. That’s the ear test.
How long: it starts as a cold, then the bark arrives, nearly always at night. It’s usually worst on the second and third nights and better within 48 hours for most children, though the cough can drag on for a few weeks. Fewer than one child in a hundred with croup has the severe kind.
What helps:
- A steroid to shrink the swelling. A doctor who sees a child with croup will usually give one dose of a steroid by mouth, and the sicker the child, the more it matters. It starts working within 2 to 3 hours and lasts a day or two, which covers the worst night. In trials of nearly 6,000 children it roughly halved the chance of needing to come back or be admitted. One dose is normally all it takes.
- Oxygen and adrenaline, if it’s severe. A child with stridor at rest and hard breathing may be given oxygen and adrenaline through a nebuliser mask, which opens the windpipe within half an hour. It wears off in about 2 hours, so the child is watched for a few hours afterwards.
- Calm and upright. Crying and lying flat both make the swelling harder to breathe through. Sit them up on your lap and keep your own voice level.
- Not steam. The old advice to sit in a steamy bathroom has been tested and doesn’t help croup. The NHS says not to.
Why there are no antibiotics
Antibiotics kill bacteria. All three of these are viruses, so antibiotics can’t touch them, and NICE says not to prescribe them for bronchiolitis. Your child’s own immune system clears the virus over a few days. Everything above is about keeping them breathing and drinking comfortably while it does. A doctor would only add antibiotics if a separate bacterial infection, such as pneumonia or an ear infection, had set in on top.
Watch the breathing
Whichever of the three it is, the thing to watch most is how hard your child is working to breathe. The noise matters too, especially with croup, where a rasp at rest is a sign in itself. These are the signs of hard work, and any of them means get help:
- The skin sucking in with each breath: under the ribs, between the ribs, or at the base of the neck.
- Grunting with each breath out.
- Nostrils flaring, or in a baby the head bobbing with each breath.
- Pauses in breathing. Very young babies with bronchiolitis can have pauses before any other sign.
- Blue or grey lips, tongue or skin. On brown or black skin, look at the palms, the soles, the gums and inside the eyelids.
- Breathing fast while resting, counted when they’re calm, not crying.
| Age | Faster than expected |
|---|---|
| Under 6 months | More than 60 breaths a minute |
| 6 to 12 months | More than 50 breaths a minute |
| Over 12 months | More than 40 breaths a minute |
From NICE’s guideline on fever in under-fives. Its bronchiolitis guideline treats more than 70 breaths a minute as severe.
Then watch the drinking. A child who is short of breath drinks less, and that is what tips most of them into hospital. Taking less than half to three-quarters of their usual feeds, or no wet nappy for 12 hours, is a reason to be seen the same day. The other signs are in our dehydration guide.
Looking after them at home
- Fluids, little and often. For a baby, smaller feeds more often. Saline drops or spray in the nose before a feed helps a blocked baby feed.
- Upright when awake. Breathing is easier sitting up than lying flat.
- Paracetamol or ibuprofen for discomfort or fever, not for the breathing. Paracetamol from 2 months, ibuprofen from 3 months, follow the pack. Never aspirin under 16.
- No smoke, no vape, indoors or out. Smoke makes all three worse, and it stays on clothes.
- Check on them overnight. Croup is worst at night, and bronchiolitis peaks around day 3 to 5.
- Follow the inhaler plan if you have one, from the first sign of the next cold, and see the GP or asthma nurse afterwards if the wheeze keeps coming back.
Red flags: get help now
Call your emergency number or go straight to an emergency department if your child:
- Is struggling to breathe: grunting, or the skin sucking in hard under the ribs.
- Has long pauses in their breathing.
- Has blue or grey lips, tongue or skin.
- Is floppy, very sleepy, or won’t wake or stay awake.
- Is too breathless to talk, eat or drink, or a wheeze is not improving after five puffs of the blue inhaler under the age of 5, or ten puffs over 5.
- Has croup with a rasping noise breathing in even when calm, is drooling or can’t swallow, or is very upset and can’t be calmed.
Get medical advice the same day (in the UK, your GP or NHS 111) if:
- They are breathing fast while resting, or working a bit harder than usual.
- They are feeding or drinking much less than normal, or have had no wet nappy for 12 hours.
- You think it is croup, or the rasping noise comes when they are upset.
- The blue inhaler isn’t lasting four hours, or they are too breathless to play.
- Your baby is under 3 months with a temperature of 38°C or above, or older with 39°C or above. See our fever guide.
- They are getting worse instead of better, or are very tired, irritable or not themselves.
- You are worried. That is reason enough to ask.
Be quicker to ask for a baby under 3 months, a child who was born prematurely, or one with a heart, lung or muscle condition or a weakened immune system.
Keeping it away
You can’t stop a child catching colds. You can lower the odds of the serious kind. In the UK, an RSV vaccine is offered from 28 weeks of pregnancy and protects the baby for about the first 6 months, which is when bronchiolitis hits hardest. In its first full year the number of babies under 6 months needing intensive care for RSV halved. Australia offers the same vaccine and an antibody injection for babies. There is no vaccine for the viruses behind wheeze and croup. Handwashing, washing toys, binning tissues and keeping smoke out of the house help with all three.
Common questions
Does viral-induced wheeze mean my child has asthma?
Not necessarily, and usually not. Around one child in three wheezes with colds by the age of 3, and most stop as their airways grow: about six in ten by age 6 and eight in ten by age 10. Only about one in three children with preschool wheeze goes on to an asthma diagnosis. Asthma is rarely diagnosed under 5; a child who keeps wheezing between colds, or who wheezes with exercise, is the one to talk to the GP about.
Why won’t the doctor give antibiotics?
Because bronchiolitis, viral wheeze and croup are all caused by viruses, and antibiotics only work on bacteria. Your child’s immune system clears the virus in a few days. The treatment is support while that happens: help with breathing and with feeding, and for wheeze and croup a medicine that opens or shrinks the swollen tube.
Should I sit my child in a steamy bathroom for croup?
No. It has been tested and doesn’t help croup, and the NHS advises against it. What does help is one dose of a steroid from a doctor, which shrinks the swelling within 2 to 3 hours, and keeping the child calm and upright while it works.
Does my baby with bronchiolitis need an inhaler?
No. UK guidance says not to give salbutamol, steroids or antibiotics for bronchiolitis, because the swelling is in tubes too small for an inhaler to open. What helps is support: smaller feeds more often, saline drops before feeds, upright when awake, and in hospital extra oxygen or feeding through a tube if needed. It’s worst around day 3 to 5 and the cough is gone in most babies by 3 weeks.
How do I tell wheeze from stridor?
Listen to which way the air is going. A wheeze is a whistle as your child breathes out, from narrowed tubes inside the lungs. Stridor is a harsh, rasping noise as they breathe in, from a narrowed windpipe, and it comes with croup’s barking cough. Stridor only when upset means see a doctor that day; stridor at rest means go to hospital.
Doodlebug keeps the timeline
Log each feed, each wet nappy, each dose of the inhaler and each temperature in two taps. When the doctor asks how much your baby has fed since yesterday, or how often you’ve needed the blue inhaler today, the answer is on one timeline instead of in your head. It’s free on the App Store.
Get DoodlebugSources
- NHS, Bronchiolitis, Croup and RSV vaccine.
- National Institute for Health and Care Excellence, Bronchiolitis in children: diagnosis and management (NG9); Asthma: diagnosis, monitoring and chronic asthma management (NG245), for children under 5; and Fever in under 5s (NG143), for the breathing rates.
- NHS Healthier Together, Viral induced wheeze; Frimley Healthier Together, Viral induced wheeze: advice for parents and carers; The Dudley Group NHS Foundation Trust, Viral induced wheeze.
- NHS Highland, Croup (paediatric guidelines); NHS Greater Glasgow and Clyde, Bronchiolitis guideline, Royal Hospital for Children.
- UK Health Security Agency, Newborn ICU admissions drop 50% in first full year of RSV maternal vaccine programme.
- Asthma + Lung UK, Preschool wheeze and Preschool wheeze and suspected asthma in children aged under 5.
- Cochrane, Glucocorticoids for croup in children; Canadian Paediatric Society, Acute management of croup in the emergency department.
- European Respiratory Society, Statement on preschool wheezing disorders; Panickar et al., Oral prednisolone for preschool children with acute virus-induced wheezing, and Foster et al., Oral prednisolone in preschool children with virus-associated wheeze.
- The Royal Children’s Hospital Melbourne, Bronchiolitis, Croup, Asthma and RSV; Children’s Health Queensland, Pre-school wheeze.
Doodlebug is a tracking app, not a medical service. This page is general information drawn from published guidance and is not advice about your child. Doses, inhaler plans, age limits and the name of your emergency number vary by country: follow the plan and the pack your own doctor gave you. If you are worried about your child, get medical help.