What is Wheezing and What are the Causes?

Causes and Tests for Respiratory Wheezing

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Wheezing is a common but frightening symptom that often prompts people to see their doctor. What is wheezing, what are some possible causes, and what can you expect when you see your doctor?

What is Wheezing? - Definition

Wheezing is defined as a high-pitched whistling sound that occurs with breathing. Wheezing can occur both with breathing in (inspiratory wheezing) and with breathing out (expiratory wheezing), though it is more common with breathing out.

What Causes Wheezing?

The sound of wheezing is created by a narrowing of the airways. This can be due to swelling or blockage anywhere from the throat down to the smallest airways. Some possible causes include:

  • Asthma  - The most common cause of wheezing is asthma.
  • Anaphylaxis - This is a severe allergic reaction (often due to a bee sting or eating nuts or shellfish) that causes swelling in the throat and is a medical emergency.
  • Bronchitis - Bronchitis can be both acute (lasting only a few days), or chronic (lasting weeks to months to years).
  • Bronchiolitis - This is an infection that involves the smallest airways (bronchioles) and is most common in children.
  • Inhaling (aspirating) a foreign body - Choking can sometimes cause wheezing if the object that is inhaled does not completely obstruct the airways. Often people recall choking, such as on a piece of steak or in the case of children, on other objects. But sometimes, especially when an object does not completely obstruct the airways (such as a piece of carrot), people may not remember a choking episode.
  • Pneumonia
  • COPD - Chronic obstructive pulmonary disease (COPD) such as emphysema may cause wheezing.
  • Bronchiectasis - A widening of the airways often due to childhood infections or cystic fibrosis is sometimes difficult to diagnose, and may at first be attributed to another cause of wheezing.
  • Epiglottitis - A medical emergency marked by symptoms such as fever, drooling, and sitting in an upright position in an attempt to breathe, epiglottitis is caused by an infection of the epiglottis – a small piece of cartilage attached to the end of the tongue.
  • Viral infections such as respiratory syncytial virus (RSV) – Many viral infections can cause wheezing, especially in children.
  • Lung cancer - The first symptom of lung cancer may be wheezing, making it important to identify the cause of wheezing even if the cause appears obvious.
  • Heart failure
  • Pulmonary embolism - Blood clots in the legs may break off and travel to the lungs (pulmonary emboli).
  • Acid reflux - It may not seem obvious, but acid reflux is a fairly common cause of wheezing.
  • Hypersensitivity pneumonitis – Chronic inflammation of the lungs caused by such things as moldy hay and bird droppings may have wheezing as the first symptom.
  • Medications – Especially aspirin.
  • Vocal Cord Dysfunction – Caused by one or both of the vocal cords closing unintentionally during breathing, this is also known as “vocal cord asthma.”

When to See Your Doctor

If you have been wheezing, it is important to see your doctor -- even if you feel you know the cause or have experienced wheezing in the past. In medical school, we were taught repeatedly to remember “all that wheezes is not asthma.” Even if you have been diagnosed with asthma, make sure to contact your doctor with any change in your symptoms.

Call your doctor (or 911) immediately if you are experiencing chest pains, lightheadedness, are finding it hard to catch your breath, or note a bluish tint to your lips and skin. Swelling of your face, neck, and lips could be a sign of a life-threatening allergic reaction.

Questions Your Doctor May Ask About Wheezing

The first thing your doctor will do (after making sure you are comfortable and stable) is take a thorough medical history and perform a physical exam. Some of the questions she may ask you include:

  • When did your symptoms begin?
  • Have you ever had symptoms like this before?
  • Is your wheezing worse at night or during the day?
  • Have you been stung by a bee, or have you eaten foods that may cause serious allergic reactions such as shellfish or nuts?
  • Do you have any other symptoms such as a cough, shortness of breath, chest pain, hives, swelling of your face or neck, or coughing up blood?
  • Do you have a personal or family history of asthma, eczema, lung diseases, or lung cancer?
  • Do you, or have you ever, smoked?
  • Have you choked while eating?

Evaluation of Wheezing

Tests to evaluate your wheezing and determine a cause will vary depending upon your history. Some of them may include:

  • Oximetry - To check the oxygen level in your blood.
  • A chest x-ray
  • Spirometry
  • Blood tests – Such as a white blood cell count to look for signs of infection.
  • Pulmonary function tests
  • A CT scan of your chest
  • Bronchoscopy - If your doctor is concerned that you may have aspirated (breathed in) a foreign object, or that you may have a tumor in or near your airways, she may order a bronchoscopy to take a closer look down in your airways.
  • Laryngoscopy - To look at your larynx and vocal cords.
  • Allergy testing - If she feels that you have allergies that are causing your airways to spasm.

Treatments for Wheezing

Depending on how serious your symptoms are, your doctor will first do what is necessary to make you comfortable and control your symptoms. Since there are many possible causes of wheezing, further treatment will depend on the cause of your wheezing.


Oo, S., and P. Le Souef. The wheezing child: an algorithm. Australian Family Physician. 2015. 44(6):360-4.

Sarkar, M., Madabhavi, I., Niranjan, N., and M. Dogra. Ascultation of the respiratory system. Annals of Thoracic Medicine. 2015. 10(3):158-68.

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