Coughing is a defensive reflex of the respiratory system that is activated to expel irritants from the airways. Although it can be annoying, its main function is to protect the lungs and keep them clear.

In this article, we explain what a cough is, how the cough reflex works, its phases, types, and most common causes, so you know when it's normal and when it could be a sign that something isn't right with your respiratory health.

 

What is cough?

 

Clinically, cough is defined as a sudden and explosive respiratory maneuver that arises with the objective of eliminating harmful substances present in the respiratory tract.

The cough consists of 3 phases: 

  1. Initial phase: Deep inspiration in which the glottis opens to allow air into the lungs
  2. Comprehensive phase: Contraction of the respiratory muscles with the glottis closed, which increases the pressure inside the lungs. 
  3. Expulsive phase: Sudden opening of the glottis with expulsion of air retained in the lungs.


Coughing is an essential reflex action for our survival as it prevents bronchoaspiration (accidental entry of liquid and solid substances into our lungs) and improves the cleaning of the airways to protect us from infections and harmful substances.. 

El cough reflex or cough reflex It appears in response to stimulation of specific receptors located in the respiratory tract (larynx, trachea and large bronchi), either by excessive accumulation of mucus, dryness or chemical substances..

 

Image: College of Pharmacists of Barcelona

 

The receptors send, through the vagus nerve, information about this stimulus to the medulla oblongata and pons, where a motor order is generated that goes to the respiratory muscles (diaphragm, intercostal and abdominal muscles) so that they contract, producing cough.. 

The correct functioning of the cough reflex will depend on the neurological and musculoskeletal systems..

But coughing is not just an involuntary phenomenon; it can be produced, suppressed, or regulated in intensity voluntarily.

The speed at which air comes out when coughing, in a healthy person, is between 360 and 1200 l/min

Types of cough

Cough can be classified in different ways.   


According to its duration:

  • Acute cough: Less than 3 weeks in duration. Its most common causes are upper respiratory infections, bronchitis, and allergies; and less frequently, aspiration, pneumonia, or a physiological reaction to the presence of a foreign body or substance in the airways.
  • Subacute cough: Lasts between 3 and 8 weeks. Caused by a recent viral infection.

If we look at the character of the cough we can find 2 different types of cough:

  • Dry cough: Cough without coughing. It may be caused by taking certain medications, viral infections, asthma, interstitial lung disease, and heart failure. 
  • Productive or wet cough: This is accompanied by expectoration of sputum or secretions. The characteristics of this sputum cannot guide one diagnosis or another. 

Cough could also be classified into:

  • Effective: When it is able to perform its function 
  • Ineffective: When you are not able to do it 

According to its cause:

  • Specific cough: An associated cause has been identified  
  • Cough of unexplained origin (idiopathic): if a cause cannot be established after a diagnostic study and an appropriate treatment proposal. 
  • Refractory cough: The cause is known, but it does not respond to treatment, so the cough persists. 

 

 

Author: Eva Maroto

References:

  1. Why do we have a cough? María Carretero. Official College of Pharmacists of Barcelona. 
  2. De Diego, A., Rubial, F., Fernández, I., Gonzálvez, J., Poveda, JL., Puente, L., Naberán K., Martínez, L., Trapero, M., Zozaya, N., Palanques, T., White Paper on Chronic Cough in Spain. 2022Weber Foundation, Madrid, Spain.
  3. What is the cough reflex?
  4. What is the cough reflex? Giovana Femat Roldán.  
  5. Cough 
  6. A. Martinez Mesa, B. Gomez Rodriguez, E.F. Sanchez Alvarez, J.L. Velasco Garrido, Study of the patient with chronic cough Manual of Diagnosis and Therapeutics in Pulmonology 
Return to Chronic Cough

 

 

Last updated on 25 August, 2025