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A cough is not an illness but a symptom of an illness or condition. Coughing is a common symptom of an upper respiratory tract infection (a common cold) and almost everyone has it every year. A flu-related cough usually gets better within a week or two but may also last longer. A cough is persistent if it lasts for more than 4 to 8 weeks.

Causes of persistent cough

If the cough persists after a common cold or bronchitis, it’s often the result (sequela) of a viral infection. The most common cause is sinusitis, which tends to prolong the cough. Another possible cause is asthma, which often begins with a persistent cough following an infection.

If the persistent cough has begun without prior flu symptoms, the cause is often some other pulmonary condition, many of which can cause a cough. A fairly common cause of persistent cough is reflux, where the acidic contents of the stomach may travel up to the throat and from there to the bronchi. Coughing can also be an adverse effect of some medicines.

Sometimes an examination fails to reveal the cause of a persistent cough. This state is called cough hypersensitivity syndrome, also referred to as idiopathic chronic cough, where the cough is a reflex associated with the respiratory organs. In cough hypersensitivity syndrome, the cough reflex is thought to be over-sensitized for reasons at present unknown.

When should you seek treatment?

If the cause of your persistent cough is unknown, you should see a doctor.

If the cough has lasted for a shorter period of time, the need for treatment will be determined by the other symptoms.

Seek treatment early if the cough involves any of the following symptoms:

  • persistent fever,
  • bloody sputum,
  • yellowish sputum, or
  • any other alarming symptoms.

Treatment of persistent cough

Persistent cough resulting from an illness usually disappears when the illness is cured. Honey, eucalyptus oil or any liquid that moisturises the throat and the larynx may alleviate the cough, especially when it’s related to upper respiratory infections. Cough suppressants obtained with a doctor’s prescription are not very effective.

If no cause for the cough can be found, i.e. you have idiopathic chronic cough, cough suppressants seldom help. If the cough involves a functional voice disorder, speech therapy may be useful.

Information sources: The Finnish Medical Society Duodecim: Terveysportti, Lääkärin tietokanta database

FSHS General Practitioner / 12 September 2019

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