Croup: barking cough, stridor, what helps and when to worry

Croup is a viral infection that makes the voice box and windpipe swell, so the airway narrows. It brings a barking cough like a seal, a hoarse voice and sometimes stridor, a harsh, high-pitched noise when breathing in. Most croup is mild and settles in a few days with calm, comfort and fluids, and a doctor may prescribe a steroid medicine. The sign that matters most is stridor while your child is resting and calm: that needs your local emergency number (000 in Australia, 999 in the UK, 911 in the US).

What is croup?

The Royal Children's Hospital Melbourne (RCH) says croup is caused by a virus that makes the voice box and windpipe swell, narrowing the airway and making breathing harder. Australia's healthdirect names parainfluenza, RSV, flu and COVID-19 among the viruses that can cause it, and says not every child who catches them gets croup.

Sources give slightly different age ranges:

The NHS says children under 3 months with croup may be referred to hospital. Australia's healthdirect says any baby under 6 months with signs of croup should see a doctor. For a cough in a young baby, see baby coughing at night.

What are the signs of croup?

Croup usually starts like a cold, with a fever, runny nose and cough. Then, often suddenly and often at night, your child may have:

• A barking cough. The NHS says it may sound like a seal.
• A hoarse or husky voice. The RCH describes a hoarse or gravelly voice.
• Stridor. A squeaky, harsh, high-pitched noise when breathing in, from the narrowed airway.
• Hard work breathing. In more severe croup, the skin between the ribs or under the neck sucks in with each breath.

The RCH sorts croup by how hard your child is working to breathe:

The NHS says to get an urgent GP appointment or call a health advice line (Pregnancy, Birth and Baby on 1800 882 436 in Australia, NHS 111 in the UK, your pediatrician's after-hours line in the US) if you think your child has croup, because a doctor may prescribe medicine to shorten it. The RCH says a child with severe croup may move around to find a comfortable position, often leaning forward.

When is croup worst, and how long does it last?

Croup tends to flare at night. The RCH says stridor often starts suddenly in the evening or overnight and that symptoms are often worst on the second or third night. Australia's healthdirect says symptoms usually peak on the second or third night too.

The RCH says stridor that's still there after 4 days is unusual and needs a doctor. Australia's healthdirect also says to see a doctor if stridor comes back after your child has recovered, or if mild croup has lasted more than 4 days.

What helps a child with croup at night?

1. Keep calm, and keep them calm. The RCH says breathing is usually harder when a child is upset, and the AAP says crying can make the cough and the work of breathing worse. Speak softly, dim the lights and offer a favourite toy or song.
2. Cuddle them upright. The NHS suggests sitting your child upright, trying not to let them lie down, and comforting them. A cuddle on your lap is often the easiest way.
3. Offer fluids. The RCH, the NHS and the AAP all say to keep up fluids. For a baby, offer breast or bottle feeds often.
4. Ease a fever or discomfort. The NHS says paracetamol or ibuprofen can help. Follow the label or ask a pharmacist; the NHS fever page says not to give ibuprofen to a baby under 3 months or under 5 kg, and the AAP gives ibuprofen only from 6 months.
5. Stay close and keep checking. The RCH says croup can change quickly, often at night, so stay close enough to hear your child. The NHS says to check on them regularly, including at night.
6. Sleep safely. Upright cuddles are for while your child is awake. Once a baby is asleep, put them back in their cot on their back, on a firm, flat mattress. The Lullaby Trust says not to incline, tilt or prop the mattress, cot or baby, and that doing so is unlikely to improve cold symptoms. See sleep when your baby is sick.

Skip cough medicines. The AAP says cough syrups aren't useful for croup and may do harm, and antibiotics don't help because croup is caused by a virus.

Do steam or humidifiers help croup?

No. The advice has changed:

• The RCH says steam is no longer recommended, because scientific evidence shows that mist and steam therapy, including vaporisers, don't help.
• The NHS says not to put your child in a steamy room or get them to breathe in steam.
• Australia's healthdirect says breathing in humidified air or steam isn't recommended, has no evidence of benefit and can cause burns.

The AAP's croup page says sitting in a steamy bathroom may help, but notes there are no studies proving it, and says the same of cool night air. Calm, upright cuddles and fluids are the safer first steps. Never leave hot water or a steaming device within your child's reach.

How do doctors treat croup?

Treatment depends on how severe it is.

• Mild or moderate croup. The RCH says doctors commonly prescribe steroids to reduce airway swelling. Australia's healthdirect says this may be a single dose of steroid medicine, and that children with mild or moderate croup can usually be cared for at home. Give any medicine exactly as the doctor or pharmacist directs.
• Severe croup. Australia's healthdirect says a child with severe croup should go to hospital by ambulance, where they may have adrenaline through a nebuliser and steroid medicine, then be watched for at least 4 hours. The AAP says children are watched for 3 to 4 hours after an adrenaline treatment. The RCH says a child with stridor at rest often needs close monitoring in hospital.
• No antibiotics. The RCH, the AAP and Australia's healthdirect all say antibiotics don't help, because a virus causes croup.

Australia's healthdirect says croup doesn't usually cause any long-term damage.

Could it be something other than croup?

A barking cough is very typical of croup, but other illnesses can cause noisy breathing or night coughs, and only a doctor can tell for sure.

• Spasmodic croup. Australia's healthdirect describes croup that comes on suddenly in the middle of the night without other symptoms and usually settles after about an hour. It says this is more common in children with asthma or a family history of allergy and asthma.
• Whooping cough and bronchiolitis can also cause night coughs and noisy breathing. Our baby coughing at night and bronchiolitis guides explain how they differ.

When to get help

If you're unsure which tier fits, call a health advice line (Pregnancy, Birth and Baby on 1800 882 436 in Australia, NHS 111 in the UK, your pediatrician's after-hours line in the US).

Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) now if your child:

• has stridor (a harsh noise when breathing in) while resting and calm
• is struggling to breathe, breathing very fast, grunting, or sucking in under the ribs, at the tummy or at the neck
• has blue, grey, very pale or blotchy skin, lips or tongue (on brown or black skin, check the lips, tongue, inside the cheeks, palms and soles)
• is drooling more than usual, can't swallow, or wants to sit up and lean forward rather than lie down
• is floppy, much sleepier than usual, hard to wake, unusually quiet and still, or not responding as usual
• is very upset or restless and can't be calmed
• pauses in their breathing or breathes irregularly
• has had no wet nappy or wee for 12 hours, or has a seizure
• is under 3 months and has a temperature of 38°C (100.4°F) or higher, or is 3 to 6 months old and has a temperature of 39°C (102.2°F) or higher

These come from the RCH, the NHS croup page, Australia's healthdirect and the NHS urgent-help guide. The RCH says to call an ambulance for a child who is struggling to breathe, has blue lips, or is drooling or can't swallow, and to go to hospital for stridor or sucking in while resting; we use the your local emergency number (000 in Australia, 999 in the UK, 911 in the US) tier for all of these, as our baby coughing at night guide does.

While you wait, Australia's healthdirect says to keep yourself and your child calm, and not to force your child into a different position, because they'll have chosen the one that helps them breathe. Don't drive your child to hospital yourself if they're struggling to breathe, very agitated, blue or very drowsy; call your local emergency number (000 in Australia, 999 in the UK, 911 in the US).

Get medical help today (same-day GP, after-hours doctor or a health advice line (Pregnancy, Birth and Baby on 1800 882 436 in Australia, NHS 111 in the UK, your pediatrician's after-hours line in the US)) if:

• you think your child has croup, or they have stridor only when upset
• your baby is under 6 months and has signs of croup
• symptoms are getting worse, or aren't improving after seeing a doctor
• stridor is still there after 4 days, or comes back after your child has recovered
• your child is feeding or drinking much less than usual, or has fewer wet nappies
• your child has had a temperature for 5 days or more

Talk to your GP or child-health nurse (book a visit soon) if mild croup has lasted more than 4 days, the barking cough is still there after a month, or your child keeps having croupy episodes that come on suddenly at night.

What's worth noting during croup?

Note when the barking cough and any stridor started, whether the stridor happens only when your child is upset or also at rest, and how they're feeding. A short video or sound recording of the cough or noisy breathing can help a doctor hear what you heard, but never delay getting help to make one.