Croup vs. Bronchiolitis: How to Tell Them Apart
It's midnight, your toddler is coughing like a seal — or is that wheezing? Two of the most common breathing illnesses in young children sound terrifying and get confused constantly. Here's how to tell them apart, and what to do about each.
Croup: the midnight barker
- Ages: 6 months to 3 years, classically
- Sound: harsh barking cough like a seal, hoarse voice, high-pitched squeak breathing in (stridor)
- Timing: often strikes suddenly at night; worse when crying or agitated
- Cause: viral swelling of the voice box and windpipe
Home care for mild croup: stay calm (your calm is contagious — crying worsens stridor), try cool night air or a steamy bathroom, offer fluids. Get care promptly for stridor at rest, retractions, or visible hard work breathing — the ER has fast-acting treatments (steroids, nebulized epinephrine).
Bronchiolitis: the wheezy infant
- Ages: under 2, mostly babies; often RSV
- Sound: wheeze breathing out, fast breathing, crackles
- Course: starts like a cold, worsens over 2–4 days with poor feeding
- Cause: viral inflammation of the small airways
Home care: saline drops + gentle suction before feeds, small frequent feeds, watch breathing closely. Babies need evaluation for retractions, fast breathing, poor feeding — and any breathing concern under 3 months old.
The cheat sheet
Barking cough + stridor in, sudden at night, toddler → think croup.
Wheeze out + fast breathing + poor feeding, developing over days, baby → think bronchiolitis.
Either way: the red flags are the same
Blue/gray lips, severe retractions or grunting, stridor at rest, can't speak or drink, pauses in breathing, limp or hard to wake — call 911 or go to the ER. Our full breathing problems guide has the complete list.
Frequently asked questions
What does croup sound like vs bronchiolitis?
Croup: barking seal-like cough with stridor (squeak) breathing IN. Bronchiolitis: wheezing/whistling breathing OUT with fast breathing, usually in babies.
Does cold air help croup?
Many parents find a few minutes of cool night air eases croupy breathing. Keep your child calm and bundled, and seek care for stridor at rest or labored breathing.
When should a wheezing baby see a doctor?
Any wheezing in a baby deserves a call to the pediatrician — promptly if there are retractions, fast breathing, poor feeding, or the baby is under 3 months old.
Reviewed by Ali Ozcan, MD, MBA
Board-certified pediatric emergency medicine physician and creator of ER4Kids. This guide reflects the same trusted, evidence-based guidance Dr. Ozcan provides to families in the emergency department.
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