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These nerve fibres are vital for keeping your airways clean. They can respond to changes in temperature, dust or other particles, acid and other irritants. There is considerable overlap in these complicated nerve pathways, thus making the diagnosis of the cause for a chronic cough particularly difficult in some cases.
The approach to sorting out the cause of a chronic cough is usually to look for the most common causes, exclude and/or treat these and then look for the more rare causes.
Generally a “chronic cough” occurs by itself without other major symptoms such as fevers, weight loss or coughing of blood, etc. If any of these are present, your doctor will first consider alternative causes.
The most common causes of a chronic cough are post-nasal drip, asthma, chronic obstructive airways disease or acid reflux. A smoker’s cough (early-morning with sputum) is not medically considered to be part of this syndrome. If you do have a “smoker’s cough”, it will usually resolve within a month after giving up smoking.
The most common causes are listed below. There are many other causes that could be considered if none of the more common causes are identified.
• Upper airway cough syndrome/Chronic post-nasal drip. Mucus produced in the nose may either be swallowed or removed by clearing the throat during the day. At night mucus may pass through the vocal cords into the upper airways. This results in irritation and inflammation of the airways and a resultant cough. The post-nasal drip may be as a result of allergies, and treatment of the allergic response in the nose may resolve the problematic cough. Symptoms may be subtle and a trial of treatment is often instituted.
• Asthma. A chronic cough may be the only symptom of asthma in some people and investigations for asthma should be done if this is suspected. Standard asthma treatment should solve the problem in this case.
• Chronic obstructive pulmonary disease (COPD). Smoking-induced airways disease (COPD/emphysema frequently result in a cough, over and above the usual "smokers cough"). Stopping smoking and specific treatment for COPD will help reduce the cough.
• Acid reflux. Symptoms of heartburn may be a pointer, but aren't always present. Chemical irritation of the airways by acid also leads to the chronic cough. A special 24-hour pH-monitoring test can be used to measure the acid levels in the oesophagus and relate these to the episodes of coughing. Treatment of the reflux with medication may be all that's required, but more extensive treatment can be employed if no response to medication is achieved and the acid reflux is confirmed to be the cause of the cough.
• Antihypertensive drugs (ACE inhibitors). Medication such as the ACE-inhibitors, a commonly used anti-hypertensive drug, has a particularly bad reputation for inducing a chronic cough. Replacement of this group of drugs with other forms of anti-hypertensives can stop a patient’s coughing.
• Chronic inflammatory conditions such as tuberculosis or HIV-associated chronic pneumonias may also present with a chronic cough. In Third World countries these diseases are given a high priority and always have to be excluded in patients with respiratory symptoms. In developed countries, these conditions may initially not be recognised as a cause of chronic cough.
• Lung cancer may induce chronic cough due to the presence of a tumour in the airway. In smokers a bronchoscopy or CT scan may be required to exclude cancer as a cause of the cough.
