Diagnosing a chronic cough begins with a detailed medical history and physical examination. Healthcare providers will inquire about the duration of the cough, associated symptoms, and any known pre-existing health conditions. They may ask about exposure to allergens, smoking habits, and whether the cough worsens during the day or at night. A chest X-ray is typically performed to exclude pneumonia or other lung diseases, and spirometry tests to assess lung function and check for asthma.

Further diagnostic tests might include a CT scan of the sinuses to rule out sinusitis or other nasal blockages that could contribute to postnasal drip, one of the common causes of chronic cough. For symptoms suggesting GERD, an upper endoscopy or a pH monitoring test may be conducted to look for signs of acid reflux. Allergen testing can be helpful if an allergic cause is suspected. These diagnostics help pinpoint the specific factors contributing to the cough, leading to a targeted treatment approach.

A chronic cough is defined as a cough that lasts for eight weeks or longer in adults, or four weeks in children. It can have various causes, with the most common being smoking, postnasal drip (mucus dripping down the throat from the back of the nose), asthma, and gastroesophageal reflux disease (GERD). Each of these conditions triggers the cough reflex for different reasons: smoking irritates the airways, postnasal drip and asthma inflame and constrict them, and GERD causes stomach acid to back up into the esophagus and irritate the throat.

Environmental factors like exposure to air pollutants, as well as chronic bronchitis (a condition leading to the inflammation of the bronchial tube linings) and certain medications such as ACE inhibitors (used for treating high blood pressure and heart conditions) can also cause a chronic cough. Identifying the underlying cause is crucial for effective treatment, which is why a comprehensive medical evaluation is often necessary when a cough persists.