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Coughing is the body's way of getting rid of foreign material or mucus that irritate the upper air passages. A cough develops when cells along the air passages get inflamed and trigger a chain of events. When this happens, air in the lungs is forced out under high pressure. A person can choose to cough, known as a voluntary process, or the body may cough on its own, in an involuntary process.

Causes of coughs

Coughs can be dry or chesty, and according to the NHS, they are classified as acute, subacute or chronic. An acute cough has been present for less than three weeks. A subacute cough resolves over three to eight weeks. Chronic, or persistent, coughs are those present for more than eight weeks.

Acute coughs can be divided into infectious and non-infectious causes.

Infectious causes of acute cough include viral upper respiratory infections (the common cold), sinus infections, acute bronchitis, pneumonia and whooping cough.

Non-infectious causes of cough include chronic conditions such as chronic obstructive pulmonary disease (COPD) including chronic bronchitis and emphysema, and asthma and environmental allergies.

Chronic coughs can be caused by:

  • Environmental irritants
  • Conditions within the lungs
  • Conditions in the upper airways
  • Conditions within the chest cavity
  • Digestive causes

Any environmental substance that irritates the upper air passages or the lungs is capable of producing a chronic cough over time. Cigarette smoke is the most common cause of a chronic cough. Other cough-producing irritants include dusts, pollens, pet dander, particulate matter, industrial chemicals and pollution, cigar and pipe smoke, and low environmental humidity.

Common causes of coughs within the lungs, include asthma, and COPD (emphysema and chronic bronchitis). Less common causes include cancer, sarcoidosis, diseases of the lung tissue and congestive heart failure with chronic fluid build-up in the lungs.

Chronic sinus infections, chronic postnasal drip, diseases of the external ear, infections of the throat, and the use of ACE inhibitor medicine for high blood pressure have all been linked with chronic coughs.

Diseases elsewhere within the chest cavity may also cause a chronic cough. They include cancer, unusual growth of a lymph node and an abnormal enlargement of the aorta, the main blood vessel leaving the heart.

An often-overlooked cause of the chronic cough is gastroesophageal reflux disease or GORD. When acid from the stomach travels up the oesophagus, it can cause irritation of the oesophagus and larynx resulting in the reflex action of a cough.

Symptoms of coughs

The causes of cough can be identified by signs and symptoms and whether it is acute or chronic.

Acute coughs are divided into infectious and non-infectious causes.

  • Signs and symptoms that suggest an infection include: fever, chills, body aches, sore throat, nausea, vomiting, headache, sinus pressure, runny nose, night sweats and postnasal drip. Sputum, or phlegm, sometimes indicates an infection is present, but it is also seen in non-infectious causes.
  • Signs and symptoms that suggest a non-infectious cause include: coughs that develop when you are exposed to certain chemicals or irritants in the environment, coughs with wheezing, coughs that routinely get worse in certain locations or during certain activities, or coughs that improve with inhalers or allergy medicine.
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