How to determine the specific cause of cough

In general, identifying the specific cause of coughing can be achieved through observation of symptom details, medical history review, physical examination, laboratory tests, and imaging studies. The specific analysis is as follows:

1. Observation of Symptom Details

Observe the duration of the cough: short-term coughs are often due to acute infections, while long-term coughs may indicate chronic conditions. Pay attention to sputum characteristics: white sputum commonly occurs in allergic reactions or chronic inflammation; yellow or purulent sputum often suggests bacterial infection; absence of sputum may point to dry-type cough disorders. Note accompanying symptoms: fever usually indicates infection; wheezing may suggest asthma; acid reflux points toward gastroesophageal reflux disease (GERD). These details help narrow down potential causes.

2. Medical History Review

Inquire about recent experiences such as colds, exposure to allergens, smoking, or inhalation of dust. Post-cold coughs are often sequelae of infection, whereas coughs following allergen exposure may be allergic in nature. Review past medical history: patients with a history of chronic bronchitis or asthma may be experiencing an exacerbation of their pre-existing condition; those with a history of gastrointestinal disorders should be evaluated for GERD-related cough.

3. Physical Examination

The physician uses a stethoscope to assess lung sounds. Wet rales may indicate pneumonia or bronchitis, while wheezing is typically associated with asthma or airway obstruction. Examine the pharynx and larynx: redness, swelling, or secretions may suggest pharyngitis causing irritative cough. A physical exam helps initially narrow the range of possible causes.

4. Laboratory Tests

Blood tests: elevated white blood cell count suggests bacterial infection; increased eosinophils may indicate allergy. Sputum culture can identify pathogenic bacteria or fungi, confirming infectious etiology. Allergen testing can determine whether cough is triggered by substances like pollen or house dust mites, providing evidence for diagnosis.

5. Imaging Studies

Chest X-ray or CT scan allows visualization of the lungs. Pulmonary inflammatory shadows typically indicate pneumonia; bronchiectasis may point to bronchiectatic disease as the cause of cough. Sinus CT scans help rule out sinusitis leading to postnasal drip, which in turn causes irritative cough, thus aiding in detection of hidden underlying causes.

In addition, pulmonary function tests may also assist in determining the cause of cough. If cough persists without improvement, timely completion of relevant evaluations is essential to avoid delayed treatment.