Croup refers to an infection of the upper airway, which becomes narrow, making it harder to breathe. Croup also causes a cough that sounds like barking.

The cough and other signs and symptoms of croup are the result of swelling and irritation around the voice box (larynx), windpipe (trachea) and bronchial tubes (bronchi). When a cough forces air through this narrowed passageway, the swollen vocal cords produce a noise like a seal barking. Taking a breath often produces a high-pitched whistling sound called stridor.

A child's healthy airway

Healthy airway

This shows a child's healthy airway.

A child with croup


When the upper airway is infected with the virus that causes croup, tissues around the voice box (larynx) and the windpipe (trachea) will swell. When a cough forces air through this narrowed passageway, it may sound like a seal barking.

Croup most often occurs in younger children. It usually isn't serious. Most children can be treated for croup at home.


Croup often begins as an ordinary cold. If there's enough swelling, irritation and coughing, a child can develop:

  • Loud barking cough that's made worse by crying and coughing, as well as anxiety and distress, setting up a cycle of worsening symptoms.
  • Fever.
  • Hoarse voice.
  • Noisy or labored breathing.

Symptoms of croup are often worse at night and usually last for 3 to 5 days.

When to see a doctor

Contact your child's health care provider if symptoms are severe, worsen, last longer than 3 to 5 days or aren't responding to home treatment.

Seek immediate medical attention if your child:

  • Makes noisy, high-pitched breathing sounds when breathing both in and out.
  • Makes high-pitched breathing sounds when not crying or upset.
  • Begins drooling or has problems swallowing.
  • Seems anxious, upset and restless or extra tired and has no energy.
  • Breathes at a faster rate than usual.
  • Struggles to breathe.
  • Develops a blue or gray tint around the nose, in or around the mouth, or on the fingernails.


Croup is usually caused by a viral infection, most often a parainfluenza virus.

Your child may get a virus by breathing infected respiratory droplets coughed or sneezed into the air. Virus particles in these droplets may also survive on toys and other surfaces. If your child touches a surface with a virus on it, and then touches the eyes, nose or mouth, an infection may follow.

Risk factors

Children between 6 months and 3 years of age have the highest risk of getting croup. Because children have small airways, they're likely to have more symptoms with croup. Croup rarely occurs in children older than 6 years of age.


Most cases of croup are mild. In a small number of children, the airway swells enough to cause problems with breathing. Rarely, a bacterial infection of the windpipe can occur in addition to the viral infection. This can result in trouble breathing and requires emergency medical care.

Only a small number of children seen in the emergency room for croup require a stay in the hospital.


To prevent croup, take the same steps you use to prevent colds and flu.

  • Frequent hand-washing with soap and water for at least 20 seconds is the most important step.
  • Keep your child away from anyone who's sick.
  • Encourage your child to cough or sneeze into the elbow.
  • Clean frequently touched surfaces.

To prevent more-serious infections that may cause croup, keep your child's vaccinations up to date. The diphtheria and Haemophilus influenzae type b (Hib) vaccines offer protection from some of the rarest — but most dangerous — upper airway infections. There isn't a vaccine yet that protects against parainfluenza viruses.

Dec 03, 2022

  1. AskMayoExpert. Croup (child). Mayo Clinic; 2021.
  2. Buttaravoli PM, et al., eds. Laryngotracheobronchitis (croup). In: Minor Emergencies. 4th ed. Elsevier: 2022. https://www.clinicalkey.com. Accessed May 9, 2022.
  3. Ferri FF. Croup (laryngotracheitis). In: Ferri's Clinical Advisor 2022. Elsevier; 2022. https://www.clinicalkey.com. Accessed May 9, 2022.
  4. Croup (laryngotracheobronchitis). Merck Manual Professional Version. https://www.merckmanuals.com/professional/pediatrics/respiratory-disorders-in-young-children/croup. Accessed May 9, 2022.
  5. Smith DK, et al. Croup: Diagnosis and management. American Family Physician. 2018;97:575.
  6. Kimberlin DW, et al. Parainfluenza viral infections. In: Red Book Online. 32nd ed. American Academy of Pediatrics; 2021. https://redbook.solutions.aap.org. Accessed May 9, 2022.
  7. Bagwell T, et al. Management of croup in the emergency department: The role of multidose nebulized epinephrine. Pediatric Emergency Care. 2017; doi:10.1097/PEC.0000000000001276.
  8. About human parainfluenza viruses (HPIVs). Centers for Disease Control and Prevention. https://www.cdc.gov/parainfluenza/about/index.html. Accessed May 9, 2022.
  9. Use caution when giving cough and cold products to kids. U.S. Food and Drug Administration. https://www.fda.gov/drugs/special-features/use-caution-when-giving-cough-and-cold-products-kids. Accessed May 9, 2022.
  10. Vaccine (shot) for diphtheria. Centers for Disease Control and Prevention. https://www.cdc.gov/vaccines/parents/diseases/diphtheria.html. Accessed May 9, 2022.
  11. Vaccine (shot) for Hib. Centers for Disease Control and Prevention. https://www.cdc.gov/vaccines/parents/diseases/hib.html. Accessed May 9, 2022.
  12. AAP Committee on Infectious Diseases. Recommendations for prevention and control of influenza in children, 2017-2018. Pediatrics. 2017; doi:10.1542/peds.2017-2550.
  13. Sullivan JE, et al. Clinical report — Fever and antipyretic use in children. Pediatrics. 2011; doi:10.1542/peds.2010-3852. Reaffirmed 2016.
  14. 201.314 Labeling of drug preparations containing salicylates. Electronic Code of Federal Regulations. https://www.ecfr.gov/cgi-bin/text-idx?SID=76be002fc0488562bf61609b21a6b11e&mc=true&node=se21.4.201_1314&rgn=div8. Accessed Feb. 22, 2018.
  15. Renaud DL (expert opinion). Mayo Clinic. Feb. 27, 2018.
  16. Baughn JM (expert opinion). Mayo Clinic. May 20, 2022.


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