Croup in babies: Why the barking cough starts at night

There’s a specific sound that stops parents cold: a cough that doesn’t sound like a cough at all, but like a seal barking somewhere down the hall. If you’ve heard it, you know exactly the moment I mean.

One minute, your baby is sleeping. The next, you hear that strange, harsh barking cough and wonder what on earth just happened.

That sound can be a sign of croup, a common childhood illness that causes swelling around the voice box and windpipe. The reassuring part? Most cases of croup are mild and get better within a few days. But because croup can sometimes make breathing difficult, knowing what to watch for, matters. 

What is croup in babies?

Croup is an infection that causes inflammation and swelling in the upper airway, particularly around the larynx (voice box) and trachea (windpipe). Viral infections are the most common cause. That swelling makes the airway narrower and because babies and young children have smaller airways than older children and adults, swelling can make breathing noisier and more difficult.

Croup is most common in young children. The American Academy of Pediatrics AAP notes that children between 3 months and 5 years are most likely to get croup,

What does croup sound like?

The classic sign is the one parents tend to remember: a barking cough that sounds like a seal. Croup often starts like a regular cold, with symptoms such as a runny nose and fever, before the characteristic barking cough and hoarse voice appear. 

Your baby may also have:

• A hoarse or raspy voice or cry
• Cold-like symptoms, such as a runny nose
• A low-grade fever
• Noisy breathing
• A high-pitched or harsh sound when breathing in, called stridor 

What is stridor?

Stridor is different from the cough. It is a harsh, high-pitched sound your baby makes while breathing in. It happens when air has difficulty moving through a narrowed upper airway. 

This is an important sound to pay attention to. A child with mild croup may have stridor when crying or active. But stridor while resting can be a sign that the airway is more swollen and that the croup is more severe. 

Why does croup get worse at night?

This is one of the biggest questions parents have after that first barking cough appears.

The short answer is: croup symptoms commonly get worse at night. Croup is typically much worse at night, with symptoms usually lasting about 3 to 7 days. The first night or two are often the worst. 

The AAP also notes that some children have spasmodic croup, which can come on suddenly in the middle of the night. A child may go to bed feeling well and wake a few hours later with a barky cough, hoarse voice, and noisy breathing. So if your baby seemed to have nothing more than a cold during the day and suddenly wakes up barking, you’re not imagining the change.

What should I do if my baby wakes up with a barking cough?

First, try to stay calm and keep your baby calm. That can be easier said than done when you’re standing in a dark nursery wondering why your baby’s cough suddenly sounds completely different.

Crying and distress can make croup symptoms and the work of breathing worse, so hold and comfort your baby while you watch how they are breathing. 

You can also:

• Keep your baby comfortable and as calm as possible.
• Offer breast milk or formula if your baby is able to drink normally.
• Watch their breathing rather than focusing only on how loud the cough sounds.
• Follow your pediatrician’s instructions if your baby has previously been diagnosed with croup.

Keeping your baby hydrated is also important. 

What about steam? Although you may have heard the old advice to sit in a steamy bathroom during a croup episode. The AAP says there are no studies proving that breathing in steam from a bathroom is effective, and doctors also note that moist air has not been shown to reduce croup symptoms. 

And skip over-the-counter cough medicines unless your child’s healthcare provider specifically recommends something. They don’t treat the airway swelling caused by croup and may be harmful in young children. 

When should I worry about my baby’s croup?

The cough itself can sound dramatic. Your baby’s breathing is the more important thing to watch.

Get urgent medical help if your baby:

• Has stridor while resting
• Is struggling to catch their breath
• Has breathing that is becoming harder or noisier
• Has bluish lips, mouth, or fingernails
• Is having difficulty drinking because of breathing problems
• Is drooling or having significant difficulty swallowing
• Becomes unusually tired from the effort of breathing 

If your baby is having significant trouble breathing, don’t wait to see whether the barking cough settles down. Seek emergency medical care.

For babies, it’s especially important to contact your pediatrician if you’re unsure about the symptoms. The AAP’s symptom guidance recommends medical evaluation for an infant under 1 year with a croupy cough. 

How is croup treated?

Most mild cases of croup can be managed at home with supportive care and monitoring. But some children need medical treatment if swelling in the airway is making breathing difficult. A healthcare provider may prescribe a steroid medicine to reduce swelling in the airway.

For children with more significant breathing problems, treatment may include nebulized epinephrine, which helps reduce airway swelling. 

Children who need epinephrine are generally observed afterward because symptoms can return as the medicine wears off. In severe cases, a child may need oxygen or hospital care. Antibiotics don’t treat typical viral croup because the illness is usually caused by a virus.

How long does croup last?

Croup usually doesn’t hang around forever. Symptoms typically last around 3 to 7 days, although the barking cough can linger longer in some children. The first few nights are often the toughest. 

If your baby’s symptoms are getting worse instead of better, the croup keeps coming back, or you’re worried about how your baby is breathing, contact your healthcare provider. Recurrent or persistent croup may need further evaluation. 

Croup at night: What parents should remember

That sudden seal-like cough can sound frightening, especially when it wakes you from a deep sleep. Remember these three things:

• Listen to the breathing, not just the cough. A barking cough is classic for croup, but stridor and difficulty breathing are more important warning signs. 
• Keep your baby calm and comfortable. Crying can make croup symptoms and the work of breathing worse. 
• Know the red flags. Stridor at rest, struggling to breathe, bluish lips or fingernails, or difficulty swallowing are reasons to seek urgent medical help. 

Conclusion

That sudden barking cough can be scary, especially when it wakes you and your baby in the middle of the night. Most cases of croup are mild and improve within a few days, but it’s important to keep an eye on how your baby is breathing. If you notice stridor while your baby is resting, trouble breathing, bluish lips, or difficulty swallowing, seek medical care right away.

And if you’re unsure, trust your gut and call your pediatrician. When it comes to your baby’s breathing, it’s always okay to ask for help.

Sources:

1. Croup overview and symptoms. MedlinePlus, National Library of Medicine (NIH). 2026. “Croup.”
2. Croup symptoms, treatment, and warning signs. MedlinePlus Medical Encyclopedia, National Library of Medicine (NIH). 2026. “Croup.”
3. Croup in young children. American Academy of Pediatrics, HealthyChildren.org. 2024. “Croup in Young Children.”
4. Severe croup and when hospital care is needed. American Academy of Pediatrics, HealthyChildren.org. 2016. “Croup: When to Call the Doctor.”