Croup in Children: Barking Cough and When to Worry
In short: Croup is a viral infection that swells the voice box and windpipe, causing a barking cough, a hoarse voice and sometimes a harsh noise when breathing in (stridor). It mostly affects children aged 6 months to 3 years, is usually worst at night, and settles within 2 to 3 days. Most children recover at home, but noisy breathing at rest, chest drawing in, drooling or unusual drowsiness need urgent medical care.
Key takeaways
Croup is usually caused by viruses, most often parainfluenza, and is most common between 6 months and 3 years of age.
The barking, seal-like cough is typically worst on the first two nights and usually improves within 2 to 3 days, though a milder cough can last about a week.
A single dose of steroid medicine prescribed by a doctor reduces airway swelling and is recommended for most children with croup, including mild cases.
Steam, cough syrups and antibiotics do not treat croup, and hot steam can cause serious scalds.
Stridor while calm, the skin between the ribs sucking in, drooling, pale or bluish lips, or a very sleepy child are signs to go to the emergency department straight away.
What is croup, and why does it sound like a bark?
Croup is a viral infection of the upper airway that makes the voice box and windpipe swell, and air squeezing through that narrowed tube produces the bark and the noisy breathing.
A young child's windpipe is small. A little swelling below the vocal cords narrows it a lot, which is why croup mostly affects toddlers and rarely troubles older children or adults with the same virus. The cough is often described as sounding like a seal or a barking dog.
Which viruses cause croup?
Parainfluenza viruses are the commonest cause. Influenza, RSV, adenovirus and some coronaviruses can also trigger it. Croup itself is not a separate germ; it is the way a young child's airway reacts to these common respiratory viruses.
Which children get croup?
Most cases happen between 6 months and 3 years, with a peak around the second year of life. Some children have croup more than once. In Malaysia, respiratory viruses circulate all year, with rises during school terms, the rainy monsoon months and when children start taska or kindergarten.
What are the symptoms of croup?
Croup usually starts like an ordinary cold, then within a day or two the child develops a barking cough, a hoarse voice and sometimes stridor, often waking at night.
How does croup usually progress?
Day 0 to 1: runny nose, mild fever, slight cough.
Night 1 to 2: sudden barking cough, hoarse voice or cry, sometimes stridor. Symptoms are often much worse between midnight and early morning.
Day 2 to 3: the bark softens and breathing becomes quieter.
Up to day 7: a looser cough and runny nose may linger.
What is stridor?
Stridor is a harsh, high-pitched sound heard when your child breathes in. It means the airway is narrowed. Stridor that only appears when your child is crying or upset is common in mild croup. Stridor that you can hear while your child is calm or asleep means the swelling is more significant and needs a doctor's assessment the same day, or urgently if your child is working hard to breathe.
Is croup the same as bronchiolitis or asthma?
No. Croup affects the upper airway, so the noise happens when breathing in. Bronchiolitis affects the small airways deep in the lungs of babies, and asthma narrows the lower airways; both tend to cause wheeze, a whistling sound when breathing out. A child can have a cough from any of these, which is why the type of noise matters.
How is croup diagnosed and treated?
Doctors diagnose croup by listening and watching your child breathe; tests are rarely needed, and most children are treated with a single dose of steroid medicine.
Will my child need an X-ray or blood test?
Usually not. The bark, the history of a cold and the way the child breathes are enough. An X-ray is reserved for children whose illness does not look like typical croup, for example if a swallowed object is suspected.
What treatment will the doctor give?
Current guidance from NICE and the Malaysian paediatric protocols supports a single dose of an oral steroid for children with croup, including mild croup. The steroid reduces swelling in the airway, shortens the illness and lowers the chance of a return visit. Your doctor will choose the medicine and dose based on your child's weight. Children with moderate to severe croup may also receive nebulised adrenaline in hospital, which works within minutes, and are observed for a few hours afterwards because its effect wears off.
Do antibiotics or cough syrup help?
No. Croup is viral, so antibiotics do not help. Cough and cold medicines are not recommended for young children and do not shorten croup.
What can you do at home?
Keeping your child calm, upright and comfortable is the most useful thing you can do, because crying makes the airway swelling and the noisy breathing worse.
For babies under 12 months
Croup under 6 months is uncommon. If your baby this young has stridor, have a doctor see them the same day.
Hold your baby upright against your chest; this position often settles breathing.
Offer breast or formula feeds more often and in smaller amounts.
Count wet nappies. Fewer than four in 24 hours is a reason to be reviewed.
For toddlers and preschoolers
Sit your child on your lap and stay calm. Children read our faces and voices closely.
Offer water or diluted fluids regularly. Cold drinks or an ice lolly can soothe a sore throat.
Give paracetamol or ibuprofen for fever or discomfort if your child is distressed, following the dose on the label for your child's age and weight.
Sleep in the same room for the first two nights so you can hear any change in breathing.
Keep your child at home from taska or school until the fever has settled and they are well enough to join in.
What not to do
Do not use steam from a kettle, a pot of boiling water or a hot shower. Studies show steam does not improve croup, and scalds in small children are a real risk.
Do not give leftover antibiotics, or cough and cold syrups.
Do not lie a child with noisy breathing flat if they prefer to sit up.
Do not smoke or vape near your child, or let others do so. Smoke irritates an already swollen airway.
Do not wait until morning if breathing is getting harder overnight.
When to see a doctor, and when not to worry
Most croup is mild, but the airway can narrow quickly at night, so knowing which signs need urgent care helps you act early without panicking over every cough.
Usually fine to manage at home
Barking cough and hoarse voice, but quiet breathing when your child is calm.
Stridor only when crying, which stops once they settle.
Your child is playing, drinking and passing urine as usual between coughing spells.
Low-grade fever that responds to paracetamol.
Book an appointment soon
Your child has had croup symptoms for more than 3 to 4 days without improving.
Croup keeps coming back, for example three or more episodes, or croup in a child older than 6 years.
The barking cough started suddenly while eating or playing with small objects, with no cold beforehand.
Your baby is under 6 months and has a hoarse cry or noisy breathing that comes and goes.
See a doctor the same day, or go to the emergency department
Stridor you can hear while your child is calm or asleep.
The skin between the ribs, below the ribcage or at the base of the neck sucks in with each breath.
Fast breathing, grunting, or your child cannot speak or cry properly.
Drooling, difficulty swallowing, or your child insists on sitting forward with the chin pushed out.
Pale, grey or bluish lips or face.
Unusual sleepiness, floppiness, confusion or agitation.
High fever with a child who looks very unwell, which can mean a rarer bacterial infection of the windpipe.
Your child cannot drink, or has had no wet nappy or urine for 8 hours or more.
If your child is struggling to breathe, call 999 or go straight to the nearest emergency department. Do not drive yourself if you need both hands to care for your child.
From Dr Nisa's clinic [DR NISA TO CONFIRM OR REWRITE]: Croup often arrives in the middle of the night, and by the time families reach me the next morning many children sound much better. That is typical of croup, not a sign that parents overreacted. What I look for is how the child breathes at rest. If the noise only comes with crying, home care is usually enough. If you can hear it while your child sleeps, please do not wait until morning. Go to the nearest emergency department.
How long is croup contagious, and can it be prevented?
The viruses that cause croup spread for a few days, mostly while your child has a fever and runny nose; handwashing and routine vaccines lower the risk but cannot remove it.
When can my child go back to taska or school?
Once the fever has gone for at least 24 hours without paracetamol and your child is eating and playing normally, they can return. A leftover mild cough is not a reason to stay home.
Which vaccines help?
No vaccine prevents all croup, but the routine Hib and diphtheria vaccines in Malaysia's National Immunisation Programme protect against dangerous infections that can look like croup, such as epiglottitis and diphtheria. A yearly flu vaccine reduces croup caused by influenza. You can read more in our guide to child vaccinations in Malaysia.
Worried about your child's cough or breathing?
I am Dr Nisa Khalil, a consultant paediatrician with more than 18 years of experience caring for children, and I see children at ParkCity Medical Centre in Desa ParkCity, Kuala Lumpur. If your child's croup keeps returning, is lasting longer than expected, or you would like a calm review of their breathing, you can book an appointment or start with an online eConsult. For a child struggling to breathe, go to the emergency department first.
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Frequently asked questions
Is croup serious?
Most croup is mild and gets better at home within a few days. Only a small minority of children with croup need admission to hospital, and very few need help with breathing. The danger is that swelling can increase at night, so it is important to know the warning signs: stridor while calm, the chest sucking in, drooling, or a drowsy child. Any of these need emergency care.
Why is croup worse at night?
Croup is often worse at night, though the exact reason is not fully understood. Natural changes in the body's steroid hormone levels, lying down, and a child waking up frightened and crying may all play a part. This is why the first two nights tend to be the hardest, and why parents often find their child sounds much better by morning.
Does cold night air help croup?
Some children seem to breathe more easily after going out into cool night air, perhaps because it calms them. There is no strong evidence that cold air treats croup. It is fine to try for a few minutes while comforting your child, but do not let it delay getting help if your child has stridor at rest or is working hard to breathe.
Can adults catch croup from a child?
Adults and older children can catch the virus that caused the croup, but they usually just get a cold or sore throat. Their airways are wider, so the same swelling does not cause a bark or stridor. Younger siblings under 3 years are the ones most likely to develop croup symptoms from the same virus.
Can a child get croup more than once?
Yes. Many children have two or three episodes before their airways grow. Croup that comes back often, appears without a cold, or continues after age 6 deserves a paediatric review. Possible reasons include reflux, allergy, asthma-like airway sensitivity or, rarely, a narrowing in the airway that a specialist may need to look at.
How long does croup last?
Croup usually lasts 2 to 3 days, with the worst symptoms on the first one or two nights. A milder cough and runny nose can continue for up to a week. If the barking cough or stridor is not improving after 3 to 4 days, or keeps getting worse, your child should see a doctor.
Medically reviewed by Dr Nisa Khalil on [DATE]. This article is general information and does not replace a consultation with your own doctor.
References
National Institute for Health and Care Excellence (NICE). Clinical Knowledge Summaries: Croup. cks.nice.org.uk/topics/croup
Ministry of Health Malaysia and Malaysian Paediatric Association. Paediatric Protocols for Malaysian Hospitals, 4th edition (2019): Viral croup.
American Academy of Pediatrics, HealthyChildren.org. Croup and Your Young Child. healthychildren.org
The Royal Children's Hospital Melbourne, Kids Health Info: Croup. rch.org.au
Gates A, et al. Glucocorticoids for croup in children. Cochrane Database of Systematic Reviews 2018. doi.org/10.1002/14651858.CD000085.pub2
Moore M, Little P. Humidified air inhalation for treating croup. Cochrane Database of Systematic Reviews 2006. doi.org/10.1002/14651858.CD002870.pub2
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