Stridor

Stridor is a high-pitched, harsh, and noisy breathing sound that indicates a narrowed or blocked airway. It is usually heard when you breathe in (inhale), but can also occur when you breathe out (exhale) or both. Stridor is always a serious symptom that requires prompt medical attention because it signals a problem with airflow to the lungs.

What is Stridor?

Stridor is a distinct, high-pitched, and often harsh breathing sound caused by turbulent airflow through a narrowed or partially blocked upper airway. Unlike snoring, which comes from the back of the throat, stridor originates higher up in the breathing passages. It is a sign that air is struggling to get past an obstruction, making it a potentially serious medical concern.

When you breathe, air normally flows smoothly through your windpipe (trachea) and voice box (larynx) into your lungs. Stridor occurs when these upper airways become too narrow, causing the air to vibrate loudly as it passes through. This sound is often described as a squeaking, whistling, or crowing noise. Most often, stridor is heard when you breathe in (inspiratory stridor), indicating a problem above the vocal cords. If it's heard when you breathe out (expiratory stridor), the blockage is usually lower in the windpipe. Stridor heard during both inhalation and exhalation (biphasic stridor) suggests a narrowing at the level of the vocal cords. It is important to distinguish stridor from other breathing sounds like wheezing. Wheezing is a musical, whistling sound typically heard when breathing out, and it usually comes from narrowed lower airways in the lungs, such as with asthma. Stridor, however, is a louder, harsher sound from the upper airway and always signals a more urgent problem with airflow.

Common causes

Stridor can result from various conditions that cause narrowing or blockage in the upper airway, ranging from infections to foreign objects. Common causes include swelling from allergic reactions, infections like croup or epiglottitis, or physical obstructions. Because the airway is vital for breathing, identifying the cause of stridor is crucial for effective treatment.

One of the most common causes of stridor in children is croup, a viral infection that causes swelling around the voice box (larynx) and windpipe (trachea). Another serious infection, epiglottitis, can also cause stridor. This condition involves swelling of the flap of tissue that covers the windpipe (epiglottis), which can quickly block the airway. In both children and adults, accidentally inhaling a foreign object, such as a piece of food or a small toy, can cause sudden stridor. Allergic reactions (anaphylaxis) can also lead to rapid swelling of the throat and tongue, resulting in stridor and severe breathing difficulty. Trauma to the throat or neck can also cause swelling and airway narrowing. Other potential causes include growths or tumors in the airway, vocal cord paralysis, or conditions present from birth (congenital conditions) like laryngomalacia, where the larynx is soft and collapses during breathing, or subglottic stenosis, a narrowing of the airway below the vocal cords. These conditions can cause chronic or intermittent stridor.

When it's serious

Stridor is always a serious symptom that requires immediate medical evaluation, as it indicates a compromised airway and potential difficulty breathing. If you or someone you know develops stridor, especially if it appears suddenly or is accompanied by other severe symptoms, seek emergency medical care right away. Prompt action can prevent life-threatening complications.

If stridor appears suddenly, especially in a child, it is a medical emergency. This is particularly true if it is accompanied by signs of severe breathing difficulty. These signs include rapid breathing, struggling to catch breath, flaring nostrils, or the skin between the ribs or at the base of the neck pulling in with each breath (retractions). Other red-flag symptoms that signal an emergency include blue or dusky discoloration of the lips, face, or skin (cyanosis), which indicates a lack of oxygen. Drooling, difficulty swallowing, or an inability to speak can suggest a severe blockage or swelling, such as with epiglottitis. Agitation or extreme tiredness can also be signs that someone is not getting enough oxygen. Never delay seeking medical help for stridor. Even if the stridor seems mild at first, it can worsen quickly. A healthcare professional needs to assess the airway immediately to determine the cause and provide appropriate treatment to ensure safe breathing.

Related conditions

Stridor is a symptom, not a disease itself, and is often associated with a range of underlying medical conditions that affect the upper airway. These conditions can vary in severity and origin, from common childhood infections to more complex structural issues. Understanding these related conditions helps explain why stridor occurs and guides diagnosis and treatment.

One of the most common conditions related to stridor, especially in young children, is croup. This viral infection causes swelling of the voice box (larynx) and windpipe (trachea), leading to a distinctive barking cough and inspiratory stridor. Another serious condition is epiglottitis, an inflammation of the epiglottis, which can rapidly block the airway and cause severe stridor, often with drooling and difficulty swallowing. Foreign body aspiration, where an object is inhaled into the airway, is a critical cause of sudden stridor. This is particularly common in toddlers. Allergic reactions, such as anaphylaxis, can cause rapid and severe swelling of the throat tissues, leading to stridor and requiring immediate emergency treatment with epinephrine. Certain conditions present from birth (congenital conditions) can also cause stridor. Laryngomalacia, for instance, is a common cause of stridor in infants, where the soft tissues of the voice box collapse inward during inhalation. Subglottic stenosis, a narrowing of the airway below the vocal cords, and vocal cord paralysis are other structural issues that can lead to stridor. Tumors or cysts in the airway, though less common, can also cause stridor by obstructing airflow.

Frequently asked questions

Is stridor always an emergency?

Yes, stridor is always considered a serious symptom that requires immediate medical evaluation. It indicates that the upper airway is narrowed or blocked, which can quickly lead to severe breathing difficulties. You should seek emergency medical care right away if you or someone you know has stridor.

How is stridor different from wheezing?

Stridor is a harsh, high-pitched sound typically heard when breathing in, originating from a narrowed upper airway (voice box or windpipe). Wheezing is a musical, whistling sound, usually heard when breathing out, and comes from narrowed lower airways in the lungs, often due to conditions like asthma.

What causes stridor in children?

In children, common causes of stridor include infections like croup or epiglottitis, inhaling a foreign object, or congenital conditions such as laryngomalacia (soft voice box) or subglottic stenosis (narrowing below vocal cords). Allergic reactions can also cause stridor in children.

Can adults get stridor?

Yes, adults can also develop stridor. Causes in adults can include inhaling a foreign object, allergic reactions, swelling from trauma to the throat, tumors or growths in the airway, or vocal cord paralysis. Like in children, adult stridor always requires prompt medical attention.

What should I do if I hear stridor?

If you hear stridor, especially if it's sudden, severe, or accompanied by difficulty breathing, blue lips, or drooling, you should seek emergency medical care immediately. Do not try to treat it at home. A healthcare professional needs to assess the airway and determine the cause.

Can stridor go away on its own?

While some mild, intermittent stridor (like that from laryngomalacia in infants) might improve as a child grows, stridor generally does not go away on its own without addressing the underlying cause. Because it signals an airway problem, it always needs medical evaluation and often treatment to resolve safely.

Sources

• MedlinePlus — Stridor
• Mayo Clinic — Stridor
• Cochrane Library — Stridor