What Is Stridor?

Learn the underlying causes

Stridor refers to the noise that is made when someone with an obstructed upper airway tries to breathe. The sound is distinctive and high-pitched. Most healthcare providers easily recognize it. You may hear stridor on inhalation, exhalation, or both.

When you hear the noise and the distinct characteristics of the sound, these can be clues as to what is causing it. Stridor is a symptom of another disease or abnormal health condition.

Symptoms and Causes

Stridor can be caused by a variety of different conditions. Depending on the cause, the symptoms may vary.


Stridor in croup, also called laryngotracheobronchitis, is often described as sounding like the barking of a seal. The cough typically gets worse at bedtime. It is most common in infants and children up to the age of about five or six. It has several causes—some of the most common causes are viruses including:

  • RSV
  • Measles
  • Adenovirus
  • Influenza

Bacterial infections can also cause croup. In addition, viral infections that cause croup can lead to secondary infections called bacterial tracheitis, which can also cause stridor.

Retropharyngeal Abscess

This condition is a complication of a bacterial throat infection. It is more likely to occur in children under six years old and may also include symptoms like a high fever and sore throat.

Peritonsillar Abscess

This is usually a complication of infection like strep throat or tonsillitis. It is more common in young adolescents and teenagers. It causes an extremely painful sore throat, fever, chills, and the inability to swallow.


This condition is very rare, especially in children who have been vaccinated. However, when it does manifest, it is life-threatening. In addition to stridor or other abnormal breathing noises, a child with epiglottis typically has uncontrollable drooling, difficulty swallowing, and high fevers.

It is specifically the H. influenza type B (HIB) vaccine that has dramatically reduced the incidence of epiglottitis.

The Inhalation of a Foreign Object

Inhaling something into the airways (that doesn't belong there) such as food or fluid can also cause stridor.

Foreign body aspiration is one of the more common causes of stridor in toddlers, and should always be suspected if symptoms consistent with stridor occur.

Severe Allergic Reaction

A life-threatening condition called anaphylaxis, which is a severe allergic reaction, can also cause stridor. Anaphylaxis can be the result of an insect sting, a food allergy, or another type of allergy. Other symptoms may include swelling of the lips or face, itching, rash, hives, runny nose, and more.


This condition causes chronic inspiratory stridor that is present at birth (congenital). This condition is a result of a softening around the tissues of the voice box. Symptoms usually occur very shortly after birth and may include difficulty feeding, acid reflux, and poor weight gain.

Symptoms are relieved when the infant is placed prone (on their tummy) and made worse when they are supine (on their back). In most cases, the baby will grow out of this condition within about a year.

Vocal Cord Paralysis

The vocal cords can become paralyzed as a result of trauma (injury or surgery) or an infection. Bilateral (both sides) vocal cord paralysis can be congenital. This is more serious than unilateral (one-sided) vocal cord paralysis.

In addition, stridor symptoms of vocal cord paralysis may include a weak cry in infants (or a weak voice in adults) or coughing or choking while eating. This condition may require surgery to correct.

Vocal Cord Lesions

These may be papillomas caused by human papillomavirus (HPV) infections or a type of nodule that prevents the vocal cords from closing properly. Nodules are usually caused by overusing your voice (screaming, straining your voice, or excessive coughing).

Other (uncommon) causes of stridor may include:

  • Subglottic stenosis
  • Tracheomalacia
  • Subglottic Hemangiomas
  • Vascular rings


As previously mentioned, stridor is not an illness but rather a symptom of an underlying health condition. Diagnosing the underlying cause of stridor is important. Before this can happen, more pressing matters may need to be addressed. For example, it is very important that your doctor check your oxygen saturation levels to make sure that your breathing difficulties do not require supplemental oxygen or other interventions.

Once it has been determined that your condition is stable and immediate problems have been addressed, your doctor may proceed to determine the underlying cause of your condition. She will most likely start with a physical examination. She will listen to your lungs, examine your ears, nose, and throat, and also ask you about your health history and current symptoms.

The following tests may also be useful in helping your doctor to determine the underlying cause of your stridor:

  • X-ray
  • Laryngoscopy
  • Bronchoscopy
  • CT scan (chest)
  • Sputum tests
  • Throat cultures


Initial treatment of stridor depends largely on how severely breathing is affected. If stridor is mild and the cause is known—such as in mild cases of croup—it can be treated at home (read below to learn the signs that indicate your child needs professional medical attention).

A cool-mist humidifier can be very helpful in treating a child with mild croup. A warm humidifier should not be used. Alternatively, you can sit with your child in a steamy bathroom for a bit. Breathing cool air (like taking your child outside in the cold for a few minutes) can also help to reduce inflammation in the airway.

Staying with your child and keeping them calm is important. Agitation can worsen stridor.

It can also be helpful to have your child drink cool liquids or suck on popsicles.

When breathing is severely affected, initial measures may include supplemental oxygen (often humidified), or breathing treatments using medications like racemic epinephrine which help to open the airway. Maintaining the airway may be necessary in severe cases through the insertion of a breathing tube and subsequent ventilation.

Once the stridor has been brought under control and adequate oxygenation established, healthcare professionals can determine the underlying cause of the stridor and begin to treat it. For example, conditions such as bacterial infections require antibiotics, and allergic reactions require epinephrine, corticosteroids, and antihistamines.

In severe cases, some conditions that cause stridor may require surgical intervention including the inhaling of a foreign object, laryngomalacia, or laryngeal or tracheal stenosis.

When to See a Doctor

Most cases of stridor should be evaluated by a doctor as soon as possible. You should seek emergency medical attention if you or your child has any of the following symptoms, or any other worrisome and unusual signs:

  • Increased difficulty breathing
  • Blue-tinged skin or lips (cyanosis)
  • Retractions (pulling or sucking in of the breathing muscles)
  • Lethargy
  • Does not have wet diapers or is not urinating
  • Has swelling of the lips or face
  • Excessive drooling
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