When to get help

Every suspected case of croup warrants a call. That is unusual advice for a mostly mild illness, and it is deliberate. The NHS says to ask for an urgent GP appointment or call NHS 111 if you think your child may have croup, because a doctor may give medicine that shortens the illness. The Irish HSE puts it more bluntly: always contact your GP or the out-of-hours service, because symptoms are usually mild but can change and get worse quickly. Babies under three months may be referred to hospital.

Call emergency services — 999 in the UK, 112 or 999 in Ireland and the EU, 911 in the US and Canada, 000 in Australia, 111 in New Zealand — if your baby:

is struggling to breathe: grunting noises, the tummy sucking in under the ribcage, or breathing that sounds different;
has blue, grey, pale or blotchy skin, lips or tongue — on brown or black skin this may be easier to see on the palms or soles;
is sleepier than normal or difficult to wake;
is unusually quiet and still, limp, floppy, or not responding as they normally do;
is very upset or restless, cannot be calmed, and is having difficulty breathing;
is drooling more than usual, finding it hard to swallow, or wants to sit rather than lie down.

healthdirect Australia adds one instruction for that last group: do not drive your child yourself if they are severely agitated, blue-tinged, struggling to breathe or very drowsy. Call for an ambulance instead.

What croup actually is

The American Academy of Pediatrics describes it as swelling of the voice box and windpipe, which narrows the airway just below the vocal cords and makes breathing noisy and difficult. It is usually caused by a viral infection. The HSE puts the commonest age under three years; the AAP says children are most likely to get croup between three months and five years, and that it becomes less common with age because the windpipe grows and swelling matters less.

What it sounds like

A barking cough that people compare to a seal.
A hoarse voice or cry.
A high-pitched, rasping sound on breathing in, called stridor.
Difficulty breathing.

Symptoms usually start as an ordinary cold with a runny nose, cough and temperature, then change character after a few days, and they are often worse at night. The HSE notes croup usually develops over a few days and can be worse at night; the AAP says most children with viral croup have a low fever, though some reach 40°C (104°F).

Stridor is the sign to watch

The AAP draws a line that is genuinely useful at 2am. Stridor is common in mild croup, especially when a baby is crying or active. Stridor while resting is a sign of more severe croup. As breathing becomes harder work, a baby may stop eating and drinking and become too tired to cough, and you may hear the stridor with every breath. That progression is the reason for the emergency list above.

Things it might be instead

The NHS lists the confusable conditions plainly. A runny nose, sneezing, cough and temperature is more likely a cold. Cold-like symptoms with wheezing, rapid breathing and poor feeding suggests bronchiolitis. Cold-like symptoms with bouts of coughing and a whoop on breathing in suggests whooping cough. Each has its own page here.

Looking after mild croup at home

Croup usually gets better on its own within about 48 hours, and the HSE says children usually improve after two days. If a clinician has confirmed it is mild:

Sit your baby upright and try not to let them lie flat.
Keep them calm. Crying makes the symptoms worse, and both the NHS and HSE list staying calm yourself as part of the treatment. It is not soft advice — distress narrows an already narrow airway.
Offer plenty of fluids, including normal milk feeds.
Check on them regularly, including at night.
Paracetamol or ibuprofen if a temperature or discomfort is bothering them. Suitability depends on age and weight, so read the label or ask a pharmacist. The HSE gives the same instruction: speak to your pharmacist and always read the label.

The steam myth

Do not put your baby in a steamy bathroom or get them to inhale steam. The NHS says this explicitly under "don't". It is the single most widely repeated piece of croup folklore, it has been handed down for generations, and current NHS advice is against it. There is also a scalding risk in carrying a distressed baby into a hot, steamy room at night.

Why it always seems to happen at night

Nobody in the guidance offers a confident mechanism, and we are not going to invent one. What the sources do say is consistent: the HSE and the NHS both note croup is often worse at night, and the HSE explicitly warns parents to expect a few nights of disturbed sleep. Practically, that means the decision you make at 9pm is not the decision you will face at 2am, and a baby who was mildly hoarse in the evening can be working hard to breathe hours later. Reassess rather than assume.

Spasmodic croup

The AAP describes a second pattern worth knowing about. Spasmodic croup is thought to be linked to allergy or reflux rather than infection. It comes on suddenly, often in the middle of the night, in a baby who went to bed well: hoarse, with stridor on breathing in and a barky cough, and usually without a fever. It can recur. The emergency signs are identical, and so is the response.

Croup in Babies