A reflex response to irritation or infection of the respiratory tract

  • More common in smokers
  • Age, gender, and genetics are not significant factors

A cough is a protective reflex action that helps to clear irritants or blockages from the airways. If sputum is produced, the cough is termed productive; if no sputum is produced, the cough is called dry.

Most coughs are due to short-term irritation of the respiratory tract and generally disappear spontaneously. In other cases, coughing may be a sign of a serious disorder of the lungs that requires medical treatment.

What are the causes?

Many coughs are caused by irritation of the upper airways (the throat and trachea), either by inhaled particles or by mucus dripping from the back of the nose. Coughing is also often caused by inflammation of the upper airways, usually as a result of a viral infection such as influenza or the common cold. Less commonly, a small foreign object, for example a peanut, is inhaled and causes violent coughing. Gastro-oesophageal reflux disease, a disorder in which acidic fluid from the stomach is regurgitated into the oesophagus, may result in a persistent cough.

More severe coughing may indicate damage to the lungs caused by inflammation associated with infections such as pneumonia, which is usually caused by bacterial infection, and acute bronchitis. In asthma, the airways in the lungs become narrowed and inflamed, producing a cough that is often worse at night or following exercise. The lungs may also be damaged by smoking, which provokes a characteristic “smoker’s cough”. Such a cough may indicate the development of chronic obstructive pulmonary disease. A smoker’s cough is frequently much worse in the morning before the chest has been cleared of mucus that has accumulated overnight. Smoking-induced damage to the cilia (tiny hairs) that line the airways interferes with the normal process by which the lungs are cleared of excess mucus.

If a long-term smoker’s cough suddenly becomes more intense or occurs more frequently than usual, this change may indicate the development of primary lung cancer and requires immediate medical investigation.

A cough may also develop as a side effect of ACE inhibitor drugs, which are used in the treatment of high blood pressure and heart disease.

What can I do?

The majority of coughs clear up after a few days without requiring treatment. However, you should consult your doctor as soon as possible if you develop a cough that persists for more than about 2 weeks. You should also seek medical advice if the cough is severe or painful, produces bloody or discoloured sputum, or is accompanied by symptoms such as chest pain or shortness of breath.

You may be able to relieve a mild cough with an over-the-counter remedy (see Cough remedies). For example, some coughs may be relieved by taking a cough suppressant, which works by inhibiting the cough reflex. However, cough suppressants should not be used to treat a productive cough because coughing is the body’s natural mechanism for clearing excess mucus from the lungs. Steam inhalation may help to loosen the mucus.

What might the doctor do?

Your doctor may be able to diagnose the cause by listening to your cough and examining your chest. Sometimes, chest X-rays or lung function tests are necessary to confirm the diagnosis. Drugs can relieve a cough, but the cause may require specific treatment. For example, antibiotics may be used to treat bacterial infection.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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