When something irritates a part of the upper airway or oesophageal tract (the UAOT), such as nasal passages, oral parts, throat, larynx, upper oesophagus or lungs, the body reacts by coughing. This reflex is how the body forcibly expels the irritation or unwanted particles from the UAOT.
Common causes of chronic cough
- Chronic infections such as sinusitis, tonsillitis, pharyngitis, laryngitis, bronchitis, and chest or dental infections, where mucus and inflammation of the throat irritate the air passages. The sticky mucus may also be inhaled into the lungs. The body responds by coughing it out.
- Smoking (or haze in the air) may cause constant irritation of the airway.
- Cancer of the throat, oral cavity, lungs or oesophagus.
- Certain antihypertensive drugs such as ACE inhibitors (look out for drugs with trade names ending with “pril”) have the side effect of increasing throat sensitivity.
- Allergies such as allergic rhinitis, throat allergy, cough variant asthma and asthma.
- Laryngopharyngeal Reflux (LPR)
LPR is a fairly common condition where the contents of the stomach regurgitate back up the oesophagus and larynx. Often, the sufferer is not aware of this reflux and it is left undiagnosed.
When this substance reaches the upper oesophagus and larynx, the acidity of the stomach content burns the larynx (which doesn’t have a protective lining, unlike the stomach and oesophagus). This reflux often leads to inflammation or ulcerations in the back of the larynx, where the larynx meets the upper oesophagus. LPR has also been known to reach the nasopharynx and Eustachian tubes in the ears, causing otitis media (middle ear infection).
LPR is often diagnosed by excluding all other possible causes of cough. Endoscopic video examination of the nasal passages, pharynx and larynx is used to exclude other causes. Such an examination can routinely pick up positive findings of LPR, if the examiner is well-experienced. These include redness, edema, inflammation, ulceration and granulation in the back of the larynx where it meets the oesophagus.
A mild case of LPR can give a very bad cough if the patient also suffers from other coughinducing conditions (such as a hypersensitive or allergic throat, upper airway infection and asthma) or is using coughinducing medication.
Most patients who suffer purely from LPR have no symptoms of gastritis or oesophageal reflux (heartburn). Also, very often, gastroscopy or barium swallow may show no abnormality. The only study to confirm LPR involves insertion of a pH (acidity) catheter through the nose to the oesophagus. The catheter is left for 24 hours to monitor the pH levels during the day and sleep. Due to the inconvenience and high cost of performing this procedure, it is not often done.
Patients suspected of having LPR would often be treated with medication to lower the gastric acid levels and advised to make lifestyle changes to reduce the reflux.
If these changes alleviate the patient’s chronic cough, LPR is usually diagnosed as the likely cause of the cough.