A wheeze is a whistling noise from the airways. Often the sound is high-pitched and occurs as a result of the airways narrowing, which causes their walls to vibrate.

People may wheeze due to a long-term condition, such as asthma or chronic obstructive pulmonary disease (COPD), or a short-term condition, such as bronchitis or pneumonia.

Expiratory wheezing occurs when a person breathes out, while inspiratory wheezing happens when they breathe in.

In this article, learn more about the differences between expiratory and inspiratory wheezing and the causes of each type.

Many different conditions can cause expiratory and inspiratory wheezing. A condition that obstructs the upper airway is more likely to cause an inspiratory wheeze, but it can also lead to expiratory wheezing.

Asthma

Asthma is a lung condition that can cause wheezing. People with acute asthma may experience both inspiratory and expiratory wheezing or just one of them.

People with asthma may also experience:

Genetics, respiratory infections, or environmental factors can cause asthma.

Chronic obstructive pulmonary disease

COPD is a lung condition. The airways of people with COPD become inflamed, which means that less air can flow into and out of the lungs, making breathing difficult.

Alongside wheezing, symptoms of COPD can include:

  • shortness of breath
  • a blue tinge to the lips or the base of the fingernails
  • fatigue
  • phlegm
  • frequent coughing

Smoking causes roughly of COPD cases. Over time, frequent exposure to air pollution and chemical fumes can also cause COPD. A few causes of COPD are genetic.

Vocal cord dysfunction

Vocal cord dysfunction, also called paradoxical vocal fold movement, happens when the vocal cords do not open as they should.

The symptoms can be similar to those of asthma and include:

  • a feeling of tightness in the throat
  • coughing
  • difficulty breathing
  • a hoarse voice or changes to the voice

Bronchitis

Coughing and a low fever are potential symptoms of bronchitis.
Coughing and a low fever are potential symptoms of bronchitis.

Respiratory infections, such as bronchitis, can cause wheezing as well as:

  • coughing that produces mucus
  • shortness of breath
  • low fever
  • chest pain

Acute bronchitis is temporary and can last from a few days to weeks. People with chronic bronchitis have repeat infections that can last for .

Pneumonia

Pneumonia is an infection of the lungs that causes them to fill with fluid. This fluid can obstruct the airways and cause wheezing. People may also notice that their breathing is shallow or rapid.

Other symptoms can include:

  • a cough that produces phlegm or, in some cases, blood
  • fever and chills
  • feeling confused
  • chest pain that worsens when breathing deeply or coughing
  • nausea

Anaphylaxis

Anaphylaxis is a severe allergic reaction to a substance or insect bite. Along with wheezing, people with anaphylaxis may find it difficult to breathe.

Other symptoms of anaphylaxis include:

  • swollen lips, tongue, or throat
  • rash or itching
  • feeling faint or dizzy
  • stomach pain

Anaphylaxis can be life-threatening, so people should seek emergency medical attention if they experience the symptoms above.

Lung cancer

Lung cancer can cause wheezing, coughing, and shortness of breath. Other signs to look out for include:

  • fatigue
  • unexplained weight loss
  • pain in the chest
  • coughing blood
  • a hoarse voice
  • recurrent infections, such as pneumonia

In severe cases, wheezing can sometimes be a sign of a collapsed airway or occur as a result of the inhalation of toxic smoke or chemicals.