Conditions & Treatments


Croup is a disease caused by a virus that leads to swelling in the airways and problems breathing.


What is croup?

Croup is a disease caused by a virus, bacteria, allergies, and inhaled irritants that leads to swelling in the airways and problems breathing. A child may have stridor, which is a high-pitched sound usually heard when the child breathes in (inspiration).

What causes croup?

Croup is most commonly caused by viruses. It is sometimes, but rarely, caused by bacteria, allergies, or reflux from the stomach. Croup is caused by a variety of different viruses. The most common virus is the parainfluenza virus. Other viruses may include:

  • Respiratory syncytial virus (RSV)

  • Influenza virus

  • Measles

  • Adenovirus

  • Enteroviruses

A child becomes infected through direct contact with a person, or the secretions of another person who is infected with the disease. The infection begins in the upper respiratory tract and then slowly spreads down the tract. Swelling affects the area around the voice box (larynx) and into the trachea.

Younger children are more affected by croup because their airways are smaller. Therefore, a small amount of swelling can cause a large amount of obstruction in their airways.

Facts about croup

  • Croup is most commonly seen in children 3 months old to 5 years.

  • The peak time for croup to occur is 2 years old.

  • Croup is seen more often in the winter.

What are the symptoms of croup

The following are the most common symptoms of croup. However, each child may experience symptoms differently. As the disease progresses down the respiratory tract, the symptoms also change and may include:

  • A runny nose, congestion, and slight cough

  • A cough develops into a "seal's bark"

  • Laryngitis

  • Fever

  • Stridor. A high-pitched sound that is usually noted as the child breathes in (inspiration), although it can also be heard as the child breathes out (expiration).

Very often, the symptoms are worse at night and wake the child from sleep. Symptoms also seem to improve in the morning but progress as the day goes on. The extent of the disease varies for each child. Most children improve in three to seven days. The symptoms of croup may resemble other conditions and medical problems. Always consult your child's doctor for a diagnosis.

How is croup diagnosed?

In addition to a complete medical history and physical examination, diagnostic procedures for croup may include:

  • Neck and chest X-rays. A diagnostic test that uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.

  • Blood tests

  • Pulse oximetry. An oximeter is a small machine that measures the amount of oxygen in the blood. To obtain this measurement, a small sensor (like a Band-Aid) is taped onto a finger or toe. When the machine is on, a small red light can be seen in the sensor. The sensor is painless and the red light does not get hot.

Treatment for croup

Specific treatment for croup will be determined by your child's doctor based on:

  • Your child's age, overall health, and medical history

  • Extent of the disease

  • Your child's tolerance for specific medications, procedures, or therapies

  • Expectations for the course of the disease

  • Your opinion or preference

In severe cases of croup, or if your child is not breathing well, hospitalization may be considered. This is sometimes hard to tell because the disease fluctuates, and your child may seem better at one moment, and then get worse the next. Your child's doctor may also order the following medications to help with the symptoms of croup:

  • Breathing treatments. These help to open up the airways.

  • Injections of medications. These help to decrease the swelling in the airways.

  • Steroids given by mouth. These help with the swelling of the airways.

Supportive treatment at home may also include:

  • Using a cool mist humidifier

  • Taking the child outside into cool, moist, night air

  • Increased fluid intake

  • Treating a fever with acetaminophen or ibuprofen, as instructed by your child's doctor

  • Keeping your child as quiet and calm as possible to help decrease the breathing effort

Treatment Programs

Massachusetts General Hospital understands that a variety of factors influence patients' health care decisions. That's just one reason why we're dedicated to ensuring patients understand their diagnosis and treatment options. Because a single option might not serve all patients, we offer a wide range of coordinated treatments and related services across the hospital. Patients should consult with their primary care doctor or other qualified health care provider for medical advice and diagnosis information.

Select a treatment program for more information:


  • Pediatric Imaging
    The Pediatric Imaging Program at Massachusetts General Hospital Imaging specializes in ensuring the safety and comfort of child patients while providing the latest technology and the expertise of specialized pediatric radiologists.
Allergy and Immunology

  • Asthma Program
    The Massachusetts General Hospital Asthma Program diagnoses and manages asthma in adults and children, and provides ongoing care to help patients effectively control their condition and enjoy a better quality of life.

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