What is Cough ?

It is a reflex that leads forceful expulsion of air from the lungs to clear the airways of mucus and irritants (e.g. dust). It is a common symptom of respiratory disease but also a consequence of problems outside of the lung. 


What causes cough?

It can be short-lived (acute), lasting less than 8 weeks or persistent (chronic) lasting 8 weeks or more. 

Causes of short-lived cough:

  • Upper respiratory tract infection
  • Lower respiratory tract (chest) infection
  • Allergic inflammation of the upper airways and sinuses (allergic rhinosinositis)
  • Exacerbation (flare-up) of underlying chronic respiratory disease (e.g. asthma, COPD, interstitial lung disease)
  • Inhalation of irritants (e.g. dust or smoke)

Causes of a persistent cough:

  • Rhinosinusitis (post-nasal drip)
  • Gastro-oesophageal reflux disease (heartburn)
  • Laryngopharangeal reflux
  • Asthma
  • Medication (e.g. angiotensin converting enzyme inhibitors for high blood pressure)
  • Other lung pathology (e.g. lung cancer, respiratory infection, bronchiectasis, COPD, interstitial lung disease)
  • Cough hypersensitivity syndrome

Associated symptoms

  • Fevers
  • Night sweats
  • Weight loss
  • Coughing blood
  • Green mucus / phlegm
  • Noisy breathing 
  • Shortness of breath
  • Difficulty swallowing 
  • Chest pain


The history often has clues to the cause of a cough. However, investigations may be needed to exclude or confirm certain conditions. 

Often a chest x-ray and lung function tests are performed. Investigations, such as sputum cultures, allergy testing, video fluoroscopy, echocardiogram, ambulatory pH studies, bronchial provocation tests, CT chest scans, or CT sinus scans may be performed if needed.  

How is it treated?

Short-lived cough often doesn’t require specific treatment and resolves on its own. Home remedies containing honey and lemon may help. 

Often the cause is multi-factorial and combination treatments are needed. 

Management is focused at treating the underlying condition:

  • Infections are treated with antibiotics or anti-fungals
  • Rhinosinusitis may need treatment with anti-inflammatory medication (e.g. intranasal steroids and anti-histamines) or antimicrobials depending on the cause
  • Gastro-oesophageal reflux may need treatment with acid suppressing medication
  • Asthma can be treated with inhaled corticosteroids
  • Medication related cough is treated by stopping the offending medication

In 10-20% of cases the cause of the cough is not identified or the cough is refractory to treatment. This is often due to cough hypersensitivity syndrome. Strategies to suppress the cough and reducing tension of laryngeal muscles are often helpful. In some cases, medication that modulate the nervous system (e.g. amitryptaline, pregabalin or gabapentin) or medication that suppress the cough reflux (e.g. opiates) are used. 

Other things that may help:

  • Quitting smoking, if you smoke, is also likely to help. 
  • Keeping the throat well hydrated – drinking frequent sips of water
  • Breathing in through the nose and out through the mouth
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