Croup

What croup is

In croup, a virus inflames the larynx (voice box) and trachea (windpipe), especially the area just below the vocal cords, called the subglottis. This is the narrowest part of a young child's airway, so even a little swelling partly blocks airflow. That causes the distinctive sounds:

• the barking cough from air pushing past swollen vocal cords
• hoarseness
• stridor, a harsh, high-pitched sound when breathing in

Croup is most common in autumn and early winter. Older children and adults get the same viruses but usually just have a cold or laryngitis, because their airways are wider.

Symptoms

1. Early: runny nose, mild fever, sore throat, like a cold.
2. After 1 to 2 days: a sudden barking cough, often waking the child at night, with a hoarse voice and sometimes stridor.
3. Course: symptoms are usually worst on the second and third nights, and improve during the day.

Most children (about 85%) have mild croup with an occasional barking cough and no stridor at rest. Fewer than 1 in 100 need intensive care.

Spasmodic croup

Some children have sudden night-time attacks of barking cough and stridor without cold symptoms or fever, often recurring. This may be linked to allergy or reflux and is managed similarly.

Causes

• Parainfluenza viruses (most common)
• RSV, influenza, adenovirus, human metapneumovirus, rhinovirus
• COVID-19, particularly the Omicron variants, caused croup in many children
• Measles in unvaccinated children

The viruses spread through coughs, sneezes and contaminated hands. Croup itself is not contagious as a condition, but the viruses that cause it are.

Conditions that can look like croup

Diagnosis

Croup is diagnosed by the characteristic cough and examination. Doctors assess severity using breathing effort, stridor, alertness and oxygen level. X-rays and swabs are not usually needed, but may be used if the diagnosis is unclear or the child is not improving.

Treatment

At home

• Stay calm and comfort your child. Crying and fear make stridor worse. Hold them upright on your lap.
• Fluids: offer drinks often.
• Fever and discomfort: acetaminophen (paracetamol) or ibuprofen (for children over 6 months) at the label dose for age and weight. Never aspirin.
• Cool air: many parents find a few minutes outside in cool night air or near an open window helps, although research on humidified air shows no clear benefit. Never use hot steam, because of burn risk.
• Sleep nearby so you can hear your child's breathing during the worst nights.
• Do not give cough and cold medicines to young children.

Medical treatment

• Dexamethasone: a single dose of a steroid by mouth is recommended for all severities of croup. It reduces swelling within 2 to 6 hours and lowers return visits and admissions.
• Nebulized epinephrine: for moderate to severe croup with stridor at rest. It works within 10 to 30 minutes and lasts about 2 hours, so children are observed for several hours afterward.
• Oxygen if levels are low.
• Hospital admission for children who need repeated epinephrine, oxygen or close monitoring. Rarely, a breathing tube is needed.

Antibiotics do not help because croup is viral. Cough syrups and decongestants are not useful.

Prevention

• Handwashing and covering coughs
• Keeping sick children home from daycare
• Routine vaccines, including flu, COVID-19 and measles (MMR), protect against some causes

Frequently asked questions

What does a croup cough sound like?

Croup causes a loud, harsh, barking cough, often compared to a seal or a dog's bark. It usually comes with a hoarse voice and sometimes a high-pitched whistling or crowing sound when breathing in, called stridor.

How long does croup last?

Croup usually lasts 3 to 7 days. Symptoms are typically worst on the second and third nights and improve during the day. The cough can linger for a few more days. See a doctor if symptoms last more than a week.

Why is croup worse at night?

Croup often worsens at night, possibly because of natural changes in hormone levels such as cortisol, lying down, and children becoming upset when they wake. That is why sudden attacks commonly happen in the middle of the night.

Is croup contagious?

The viruses that cause croup are contagious and spread through coughs, sneezes and touch. A child is most contagious during the first few days of illness, especially with fever. Other children may catch the virus but develop only a cold.

When should I take my child to the ER for croup?

Go to the ER or call 911 if your child has stridor at rest, struggles to breathe, has skin pulling in at the neck or ribs, drools, cannot swallow, turns blue or pale, or is unusually drowsy or agitated.