Croup: the barking cough that wakes babies at night
It's the middle of the night, your baby was completely fine at bedtime, and suddenly you are hearing a sound you have never heard before: a loud, barking cough, almost like a seal. It is frightening, especially the first time. But the good news is that croup is almost always manageable at home, and simply knowing what it is can help you stay calm enough to help your baby through it.
What is croup?
Croup is a viral infection that causes swelling and inflammation of the larynx (the voice box), the trachea (the windpipe), and the upper airways. That swelling narrows the airway, which is why the cough produces its distinctive hollow, barking sound, and why breathing in can become noisy. The harsh, high-pitched sound your baby makes when breathing in is called stridor, and it is one of the hallmarks of croup.
Croup is almost always caused by parainfluenza viruses, though other respiratory viruses can trigger the same pattern. It is not the same as a regular cough or chest infection. The inflammation sits in the upper airway, not deep in the lungs, which is an important distinction when it comes to treatment.
Who gets croup, and when?
Croup is most common in children between six months and three years old, with the peak around age two. Younger babies, particularly those under six months, can get croup too, and tend to be monitored more closely when they do because their airways are smaller. It is more common in autumn and winter, when the parainfluenza viruses that cause it circulate most.
Boys are slightly more likely to get croup than girls. Some children seem prone to repeated episodes, which can be alarming for parents but is usually still caused by different viruses each time, not a sign of a more serious underlying problem.
The typical pattern: why nights are worst
One of the most reassuring things to know about croup is that it follows a predictable pattern. Your baby or toddler will often go to bed seeming fine, or with just a mild runny nose. Then, in the early hours of the morning, typically between midnight and 4am, they wake up with the barking cough and possibly stridor.
During the day, croup often eases. The symptoms return the following night, sometimes a little better, sometimes about the same. Most children see improvement over two to three nights, with each night being a little more manageable than the last.
Cool air tends to relieve airway swelling quickly. This is why parents who bring their baby to the car park or the back garden in the night air often find the stridor improves within minutes. It is not your imagination: the physiology backs it up.
Caring for your baby at night
The most important thing you can do is stay calm. Your baby will pick up on your anxiety, and crying and distress make stridor worse by causing the inflamed airway to tighten further. Speaking quietly, holding your baby upright on your lap, and keeping the room peaceful all help.
Sitting your baby upright helps gravity keep the airway as open as possible. Cool, fresh air is your most effective tool: open a window in the room, or briefly take your baby into the cool night air outside (wrapped warmly). Many parents find the stridor eases noticeably within five to ten minutes.
You may have heard that steam from a hot shower can help. The NHS no longer recommends this approach. The evidence that steam helps is weak, and there is a real risk of scalding from hot steam in a small bathroom. Stick to cool air instead. Do not leave your baby alone while they are having a croup episode, and keep them as calm and comfortable as you can.
Signs that croup has become an emergency
Croup is usually mild, but in a small number of children it can cause severe narrowing of the airway that needs urgent treatment. Call 999 immediately if your baby:
- Has lips, skin or tongue that look blue or grey
- Is struggling to breathe and you can see their chest or the skin at the base of their throat pulling in sharply with every breath (retractions)
- Has stridor when they are completely calm and resting, not just when crying or coughing
- Cannot swallow or is drooling unusually
- Seems exhausted, floppy or too tired to breathe properly
These are signs of severe croup that need hospital treatment immediately. Do not wait to see if things improve on their own if any of these are present.
Treatment in hospital
If your baby needs hospital care for croup, the first treatment is usually a single dose of a corticosteroid, most commonly dexamethasone or prednisolone. These medicines reduce the swelling in the airway and typically start working within an hour. They are safe, effective, and dramatically reduce how many children need further treatment.
In more severe cases, a nebulised adrenaline treatment (delivered through a mask or mouthpiece as a fine mist) may also be given to open the airway quickly. Most children respond well and are well enough to go home the same day. Hospital admissions for croup overnight are sometimes needed for observation, but serious complications are uncommon.
How long does croup last?
Mild croup usually clears within three to five days. The barking cough may linger a little longer as the swelling in the airway settles fully, even once the nights are easier. This is normal and not a sign that things are getting worse.
If your baby has had croup two or three times or more, it is worth mentioning to your GP. Recurrent croup is often still caused by different viral infections each time, but your doctor may want to check there are no other reasons for repeated airway narrowing, such as a structural issue or reflux.
Frequently asked questions
What does croup sound like?
The cough in croup is very distinctive: a loud, hollow bark, often compared to a seal or a small dog. Your baby may also have stridor, a harsh, high-pitched sound when they breathe in (not when they breathe out). If you are not sure whether what you are hearing is croup, searching for "croup cough audio" online can help you recognise it. Most parents who hear it once recognise it immediately if it happens again.
Should I take my baby outside at night for croup?
Yes, briefly. Cool night air often helps reduce airway swelling and ease the stridor within minutes. Hold your baby upright, wrap them warmly in a blanket, and spend five to ten minutes breathing in the cool air outside. It is one of the most effective things you can do at home and the improvement can feel almost immediate.
When does croup become an emergency?
If your baby has stridor when they are completely calm and resting (not only when they are upset or crying), if their lips or skin look blue or grey, if you can see their chest or throat visibly straining inward with each breath, or if they seem too exhausted to breathe comfortably, call 999 without delay. These signs mean the airway is severely narrowed and needs emergency treatment.
How long does croup last?
Most cases of croup resolve within three to five days. Typically nights two and three are the hardest, and things improve from there. The cough may persist for a few more days after the worst is over. If your baby is still getting worse after five days, or if they develop a very high fever on top of the croup symptoms, contact your GP.
Can babies get croup more than once?
Yes. Several different viruses can cause the same pattern of airway swelling, so children can have croup more than once. Having one episode does not protect against future ones. If your baby has had croup two or three times, it is worth mentioning to your GP, who may want to rule out other contributing factors.
Is croup contagious?
The viruses that cause croup are contagious and spread in the same way as cold viruses: through droplets from coughs and sneezes, and from touching contaminated surfaces and then touching the face. Croup itself (the specific airway inflammation) is not directly transmitted, but the underlying virus can cause illness in others. Regular handwashing is the most practical way to limit spread within the household.
Know when to worry, know when to wait
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