A sudden croup cough that sounds like a seal, noisy breathing that wakes everyone up, a toddler sitting bolt upright and looking startled: croup can feel dramatic, even when it stays mild. Most episodes are short and respond well to a few targeted measures.
What helps parents most is a clear map: why croup happens, how to spot the signs that mean “watch closely” versus “get help now”, what clinicians usually do (and why steroids are so often mentioned), and how long recovery typically takes.
What croup is and why it sounds so loud
Croup is most often a viral infection that inflames the upper airway, mainly the larynx (voice box) and the trachea (windpipe). You may hear laryngotracheitis or acute laryngotracheobronchitis. In young children, swelling just below the vocal cords (the subglottic area) narrows the airway.
That narrowing leads to:
- Barking cough (the “seal-like” cough)
- Inspiratory stridor: a harsh sound mainly when breathing in
You might also see retractions (skin pulling in at the neck or between/under the ribs), meaning extra breathing effort. Crying often makes stridor louder because airflow becomes faster and more turbulent.
Why croup is common in toddlers and worse at night
Croup is most frequent between 6 months and 5 years (peak 6 months to 3 years). Older children have wider airways, so the same swelling makes less noise.
Nighttime worsening is typical: children are tired, lie flat, and agitation amplifies the sound. Cool, dry air can also irritate an already inflamed airway.
Causes of croup: viruses first
Viral triggers
Most croup is caused by viruses, especially parainfluenza virus (types 1 and 2). Others include RSV, influenza, adenovirus, rhinovirus, and SARS-CoV-2. Often it begins like a cold, then the barky cough and hoarseness appear.
Spread and incubation
Viruses spread through droplets and hands/surfaces. Incubation is often 2 to 6 days.
Bacterial illnesses that can look similar
Uncommon, but important:
- Bacterial tracheitis: may start like croup, then worsen quickly with high fever and a very unwell child.
- Epiglottitis: rare, but a true emergency (see below).
Irritants and reflux
Repeated or disproportionate croup can be influenced by:
- Gastroesophageal reflux (GER) irritating the larynx
- tobacco smoke exposure (including particles on clothes)
- strong fragrances, pollution, very dry indoor air
Types of croup you may hear about
Viral croup (classic)
Cold symptoms first, then barking cough, hoarseness, and stridor that fluctuates, often worse overnight.
Spasmodic croup
Often sudden nighttime onset, little fever, and a child who seems well during the day. Episodes can recur, with symptom-free gaps, airway hyperreactivity, irritants, allergy tendency, and reflux are often discussed.
Atypical or severe presentations
If episodes are very frequent, unusually severe, or outside preschool years, clinicians may consider triggers and (less often) structural airway differences.
Croup symptoms: what parents notice
The “classic trio”
With croup, parents commonly notice:
- barking cough
- hoarse voice (or a rougher cry in babies)
- inspiratory stridor
Feeding changes
Swallowing can feel uncomfortable. Babies may take shorter feeds or pause more. Light drooling can occur with throat irritation, heavy drooling plus refusal to swallow is more concerning.
Fever and cold symptoms
Viral croup often comes with congestion and mild-to-moderate fever. Spasmodic croup often has little or no fever. High fever doesn’t exclude croup, but it increases the need to check for another illness too.
Stridor: with activity or at rest?
A practical severity clue:
- Stridor only with crying/activity: often mild.
- Stridor at rest or during sleep: more concerning: seek urgent assessment.
Signs breathing is hard work
Watch for:
- retractions
- fast breathing, nasal flaring
- difficulty speaking/crying normally
Cyanosis and dehydration
- Blue lips/face (cyanosis): emergency.
- Dehydration signs: fewer wet diapers, very dry mouth, no tears, refusing fluids.
Severity levels: what “mild” and “severe” mean
Mild croup
Barking cough and hoarseness, stridor only with activity, little or no retractions. Many children can be cared for at home, often after a clinician advises a steroid dose.
Moderate croup
Intermittent stridor at rest, clear retractions, anxiety from breathing effort. This usually deserves same-day assessment.
Severe croup
Persistent stridor at rest, marked retractions (including above the breastbone), significant distress, possible low oxygen. Urgent evaluation is needed.
Impending respiratory failure (rare)
Unusual sleepiness, exhaustion, quieter breath sounds (less air moving), or cyanosis: call emergency services.
Recurrent croup
Repeated episodes (for example, 3+ in a year), severe attacks, or croup outside typical ages may prompt discussion about reflux, allergy tendency, airway reactivity, or ENT review.
Croup or something else? Key comparisons
Croup vs asthma/bronchiolitis
- Croup: stridor (breathing in), barky cough, hoarseness.
- Asthma/bronchiolitis: wheeze (often breathing out), chesty cough, fast breathing.
Croup vs foreign body aspiration
Sudden onset during eating/play without a cold suggests aspiration: urgent assessment.
Croup vs epiglottitis (emergency)
Typical features: sudden severe sore throat, high fever, drooling, trouble swallowing, child leaning forward and refusing to lie down. Do not look in the throat, call emergency services.
How clinicians diagnose croup
Diagnosis is usually clinical: the history plus the exam.
Clinicians assess work of breathing, hydration, and often oxygen saturation. Some teams use the Westley croup score (stridor, retractions, air entry, consciousness, cyanosis). X-rays and viral tests are not routine when the picture is typical.
Home care for mild croup
When croup flares, aim to reduce breathing effort and agitation.
- Hold your child upright, keep the room quiet.
- Offer small sips of fluid (or shorter, more frequent feeds).
- For babies with a blocked nose: saline drops/spray and gentle suction when needed.
Humidified air has mixed evidence. Avoid hot steam (burn risk). If you use a humidifier, clean it often.
For fever/discomfort, acetaminophen (paracetamol) or ibuprofen can be used in weight-appropriate doses.
Avoid over-the-counter cough/cold medicines for young children unless specifically advised, and avoid antibiotics for typical viral croup.
Medical treatment for croup
Corticosteroids
A single dose of dexamethasone is standard care across croup severities because it reduces airway swelling. A commonly used dose is 0.6 mg/kg (maximum often around 10 mg), given by mouth or injection. Nebulized budesonide may be used if oral medication isn’t feasible.
Nebulized epinephrine
For moderate to severe croup, nebulized epinephrine can improve airflow quickly. Because symptoms may return as it wears off, monitoring for a few hours is typical.
Supportive care in hospital
Oxygen is used if saturation is low or breathing work is high. IV fluids may be needed if drinking is difficult. Heliox is occasionally used in selected severe cases.
Antibiotics are discussed when a bacterial illness is suspected (for example, bacterial tracheitis).
When to seek urgent or emergency care
Call emergency services immediately if
- blue lips/face (cyanosis)
- pauses in breathing
- severe retractions or obvious struggle for each breath
- unusual sleepiness or poor responsiveness
Seek urgent medical assessment if
- stridor at rest
- worsening work of breathing or very fast breathing
- drooling or trouble swallowing
- child cannot drink, or looks pale/gray and very unwell
- high fever with a seriously ill appearance
- symptoms persist or worsen after steroids
Babies under 3 months
Any breathing difficulty, fever, or marked drop in feeding deserves prompt medical evaluation.
Recovery, contagiousness, and return to daycare
Many croup episodes peak over the first 1 to 2 nights.
- Day 0 to 1: cold symptoms, hoarseness
- Day 2 to 3: barking cough/stridor may peak
- Day 4 to 7: gradual improvement (cough/hoarseness can linger)
Because croup is usually viral, contagiousness is often highest in the first few days and while fever is present.
Return to daycare is reasonable when your child is fever-free for 24 hours without fever reducers, breathes comfortably at rest, drinks adequately, and can participate in normal activities.
Persistent hoarseness beyond about three weeks, or recurrent croup, should be discussed with a clinician, sometimes ENT review is suggested.
Prevention
- Handwashing and cleaning shared surfaces reduce viral spread.
- Avoid tobacco smoke exposure.
- Air rooms daily, aim for indoor air that is comfortable, not overly dry.
If croup keeps returning, your pediatrician may ask about reflux and allergy symptoms, then suggest targeted steps.
Key takeaways
- Croup is a common upper-airway illness in young children, it often worsens at night and can sound frightening even when mild.
- Barking cough, hoarse voice, and inspiratory stridor are typical, stridor at rest needs urgent medical assessment.
- Dexamethasone is commonly used to reduce swelling, nebulized epinephrine is used for moderate to severe croup with monitoring.
- Emergency care is needed for cyanosis, pauses in breathing, severe retractions, drooling with trouble swallowing, or unusual sleepiness.
- Most children improve over a few days, recurrent croup may be influenced by irritants or reflux and deserves discussion with a professional. Parents can also download the Heloa app for personalized tips and free child health questionnaires.
Questions Parents Ask
Can my child sleep with croup — and is it OK to lie them down?
Yes, most children with mild croup can sleep. Many parents find their child rests more comfortably slightly upright (for example, in your arms or with the head of the mattress gently elevated). The priority is safe sleep: babies should still sleep on a firm, flat surface, on their back, with no pillows or loose bedding. If noisy breathing settles when your child is calm and their color stays normal, that’s reassuring. If stridor continues at rest during sleep, or breathing looks hard work, urgent assessment is a good idea.
Why does my child keep getting croup?
Recurrent episodes can happen, and it doesn’t mean you’ve done anything wrong. Some children simply have more sensitive upper airways. Triggers often discussed include frequent viral exposure (especially in daycare), irritants like tobacco smoke or strong fragrances, very dry indoor air, and sometimes reflux. If episodes are frequent (for example, several in a year), unusually severe, or happening outside the typical preschool years, you can ask your clinician whether an ENT review or evaluation for reflux/allergies makes sense.
How long is croup contagious — and when can they go back to daycare?
Croup is usually caused by a virus, so it tends to be most contagious in the first few days and while fever is present. Daycare is generally reasonable once your child has been fever-free for 24 hours (without fever reducers), is breathing comfortably at rest, is drinking well, and has the energy to join normal activities.
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