Cough Explained

Specialty:Infectious disease
Pronounce: Latin: tussis

A cough is a sudden expulsion of air through the large breathing passages that can help clear them of fluids, irritants, foreign particles and microbes. As a protective reflex, coughing can be repetitive with the cough reflex following three phases: an inhalation, a forced exhalation against a closed glottis, and a violent release of air from the lungs following opening of the glottis, usually accompanied by a distinctive sound.[1]






Differential diagnosis

A cough in children may be either a normal physiological reflex or due to an underlying cause. In healthy children it may be normal in the absence of any disease to cough ten times a day. The most common cause of an acute or subacute cough is a viral respiratory tract infection. In adults with a chronic cough, i.e. a cough longer than 8 weeks, more than 90% of cases are due to post-nasal drip, asthma, eosinophilic bronchitis, and gastroesophageal reflux disease. The causes of chronic cough are similar in children with the addition of bacterial bronchitis.




Reactive airway disease




Gastroesophageal reflux

In people with unexplained cough, gastroesophageal reflux disease should be considered. This occurs when acidic contents of the stomach come back up into the esophagus. Symptoms usually associated with GERD include heartburn, sour taste in the mouth, or a feeling of acid reflux in the chest, although, more than half of the people with cough from GERD don’t have any other symptoms. An esophageal pH monitor can confirm the diagnosis of GERD. Sometimes GERD can complicate respiratory ailments related to cough, such as asthma or bronchitis. The treatment involves anti-acid medications and lifestyle changes with surgery indicated in cases not manageable with conservative measures.

Air pollution


Foreign body


Angiotensin-converting enzyme inhibitor

Angiotensin-converting enzyme (ACE) inhibitors are drugs used in diabetics, heart disease, and high blood pressure. In 5-35%[6] of the people who take it, it can cause them to have a cough as a side effect. Cessation of ACE Inhibitor use is the only way to stop the cough. Such medicines for hypertension are very common in use such as ramipril and quinapril. There are cases of "cough of unknown origin" who had resolution with stopping the drug.[7]

Psychogenic cough

A psychogenic cough, "habit cough" or "tic cough" coughing for no apparent reason may be the cause in the absence of a physical problem. In these instances, emotional and psychological problems are suspected. However, other illnesses have to be ruled out before a firm diagnosis of psychogenic cough is made.


Neurogenic cough







A cough is a protective reflex in healthy individuals which is influenced by psychological factors. The cough reflex is initiated by stimulation of two different classes of afferent nerves, namely the myelinated rapidly adapting receptors, and nonmyelinated C-fibers with endings in the lungs. However it is not certain that the stimulation of nonmyelinated C-fibers leads to cough with a reflex as it is meant in physiology (with its own five components): this stimulation may cause mast cells degranulation (through an asso-assonic reflex) and edema which may work as a stimulus for rapidly adapting receptors.

Diagnostic approach





A cough can be classified by its duration, character, quality, and timing. The duration can be either acute (of sudden onset) if it is present less than three weeks, subacute if it is present between three or eight weeks, and chronic when lasting longer than eight weeks. A cough can be non-productive (dry) or productive (when phlegm is produced that may be coughed up as sputum). It may occur only at night (then called nocturnal cough), during both night and day, or just during the day.

A number of characteristic coughs exist. While these have not been found to be diagnostically useful in adults, they are of use in children. A barky cough is part of the common presentation of croup.[13] A staccato cough has been classically described with neonatal chlamydial pneumonia.[14]



According to the American Academy of Pediatrics the use of cough medicine to relieve cough symptoms is supported by little evidence and thus not recommended for treating cough symptoms in children. There is tentative evidence that the use of honey is better than no treatment or diphenhydramine in decreasing coughing.[16] It does not alleviate coughing to the same extent as dextromethorphan but it shortens the cough duration better than placebo and salbutamol. A trial of antibiotics or inhaled corticosteroids may be tried in children with a chronic cough in an attempt to treat protracted bacterial bronchitis or asthma respectively. There is insufficient evidence to recommend treating children who have a cough that is not related to a specific condition with inhaled anti-cholinergics.[17]


A cough is the most common reason for visiting a primary care physician in the United States.[18]

Other animals

Marine mammals such as dolphins cannot cough.[19] Domestic animals such as dogs and cats can cough, because of diseases, allergies, dust or choking.[20] In particular, cats are known for coughing before spitting up a hairball.


See also

Further reading

Notes and References

  1. Chung KF, Pavord ID . Prevalence, pathogenesis, and causes of chronic cough . Lancet . 371 . 9621 . 1364–74 . April 2008 . 18424325 . 10.1016/S0140-6736(08)60595-4 .
  2. Pavord ID, Chung KF . Management of chronic cough . Lancet . 371 . 9621 . 1375–84 . April 2008 . 18424326 . 10.1016/S0140-6736(08)60596-6 .
  3. News: Cystocele (Prolapsed Bladder) NIDDK. National Institute of Diabetes and Digestive and Kidney Diseases. 2017-12-02.
  4. Dicpinigaitis PV, Colice GL, Goolsby MJ, Rogg GI, Spector SL, Winther B . Acute cough: a diagnostic and therapeutic challenge . Cough . 5 . 11 . 2009 . 20015366 . 2802352 . 10.1186/1745-9974-5-11 . In the vast majority of cases, acute cough is due to acute viral upper respiratory tract infection (URTI), i.e., the common cold. .
  5. Braman SS . Postinfectious cough: ACCP evidence-based clinical practice guidelines . Chest . 129 . 1 Suppl . 138S–146S . January 2006 . 16428703 . 10.1378/chest.129.1_suppl.138S .
  6. Dicpinigaitis PV . Angiotensin-converting enzyme inhibitor-induced cough: ACCP evidence-based clinical practice guidelines . Chest . 129 . 1 Suppl . 169S–173S . January 2006 . 16428706 . 10.1378/chest.129.1_suppl.169S .
  8. Irwin RS, Glomb WB, Chang AB . Habit cough, tic cough, and psychogenic cough in adult and pediatric populations: ACCP evidence-based clinical practice guidelines . Chest . 129 . 1 Suppl . 174S–179S . January 2006 . 16428707 . 10.1378/chest.129.1_suppl.174S .
  9. Gibson PG, Ryan NM . Cough pharmacotherapy: current and future status . Expert Opinion on Pharmacotherapy . 12 . 11 . 1745–1755 . August 2011 . 21524236 . 10.1517/14656566.2011.576249 .
  10. NCBI » Bookshelf » Clinical Methods » The Pulmonary System » Cough and Sputum Production
  11. Web site: C.Chronic Cough . 2010-10-10 . dead . . 2010-10-01 . National Lung Health Education Program > C. Chronic Cough
  12. Web site: Cough in Adults. Noah Lechtzin. Merck Manuals. 2017-04-07. Last full review/revision July 2016
  13. Bjornson CL, Johnson DW . Croup in the paediatric emergency department . Paediatr Child Health . 12 . 6 . 473–477 . July 2007 . 19030411 . 2528757 . 10.1093/pch/12.6.473.
  14. Miller KE . Diagnosis and treatment of Chlamydia trachomatis infection . Am Fam Physician . 73 . 8 . 1411–6 . April 2006 . 16669564 .
  15. Thompson . M. . Vodicka . T. A. . Blair . P. S. . Buckley . D. I. . Heneghan . C. . Hay . A. D. . Duration of symptoms of respiratory tract infections in children: systematic review . BMJ . 11 December 2013 . 347 . dec11 1 . f7027–f7027 . 10.1136/bmj.f7027 . 24335668 . 3898587 .
  16. Oduwole . O . Udoh . EE . Oyo-Ita . A . Meremikwu . MM . Honey for acute cough in children. . The Cochrane Database of Systematic Reviews . 10 April 2018 . 4 . CD007094 . 10.1002/14651858.CD007094.pub5 . 29633783. 6513626 .
  17. Chang. A. B.. McKean. M.. Morris. P.. 2004. Inhaled anti-cholinergics for prolonged non-specific cough in children. The Cochrane Database of Systematic Reviews. 1. CD004358. 10.1002/14651858.CD004358.pub2. 1469-493X. 14974067.
  18. Goldsobel AB, Chipps BE . Cough in the pediatric population . J. Pediatr. . 156 . 3 . 352–358.e1 . March 2010 . 20176183 . 10.1016/j.jpeds.2009.12.004 .
  19. Woodard . James C. . Zam . Stephen G. . Caldwell . David K. . Caldwell . Melba C. . Some Parasitic Diseases of Dolphins . Pathologia Veterinaria . 29 August 2016 . 6 . 3 . 257–272 . 10.1177/030098586900600307.
  20. News: Is It Normal for Cats To Cough?. Pet Health Network. 2018-04-23.
  21. News: Coughing in horses explained. Your Horse Magazine. 2018-04-23.