Phlegm, produced by mucous glands in the respiratory tract, moisturizes and traps dust, bacteria, and other harmful agents. When excess phlegm accumulates due to inflammation, the body triggers a cough reflex to expel it.

Doctor Dang Thi Mai Khue, from the Department of Internal Medicine at Tam Anh General Hospital in TP HCM, explains that the causes of a phlegm-producing cough vary depending on the color and consistency of the phlegm, the frequency of the cough, and accompanying symptoms.

The common cold, primarily caused by the rhinovirus, leads to inflammation of the nasal sinuses, throat, and airways, increasing phlegm production. Initially clear or white, phlegm can turn yellow or green as the immune system responds to the infection. Coughs due to colds usually resolve within a week.

Influenza, a more severe viral infection than the common cold, affects both the upper and lower respiratory tracts, causing a persistent cough. The phlegm produced can be thick, yellow, or green, especially with a bacterial superinfection. Unlike a cold, the flu often involves high fever, chills, body aches, and severe fatigue. Yellow or green phlegm may indicate a bacterial superinfection.

Acute bronchitis occurs when the bronchial tubes become inflamed due to a viral or bacterial infection, leading to increased phlegm production and a persistent cough. Phlegm may initially be clear or white, then turn yellow or green as the infection progresses. Some individuals may experience a lingering cough even after the infection subsides.

Doctor Mai Khue consults with a respiratory patient. Photo: Tam Anh General Clinic, District 7

Doctor Mai Khue consults with a respiratory patient. Photo: Tam Anh General Clinic, District 7

Pneumonia, a severe lung infection, causes inflammation and filling of the air sacs (alveoli) with pus or phlegm, resulting in a severe cough, shortness of breath, and chest pain. Phlegm is typically thick, yellow, green, or brown (if blood is present). Bacterial pneumonia requires prompt antibiotic treatment, while viral pneumonia may improve with supportive care and antiviral medication if necessary.

Chronic obstructive pulmonary disease (COPD), encompassing chronic bronchitis and emphysema, often results from smoking or prolonged exposure to smoke and dust. A persistent cough with large amounts of phlegm, especially in the morning, is a typical symptom. Phlegm can be white, yellow, or green. In advanced stages, patients may experience shortness of breath and severely reduced lung function. Increased phlegm or changes in its color are signs of a COPD exacerbation, requiring specialist consultation.

Bronchiectasis, a condition of permanently widened bronchial tubes, leads to mucus accumulation and an increased risk of lung infections, causing a persistent cough with thick, typically yellow or green phlegm. Patients are at high risk for frequent respiratory infections, with common symptoms including chest tightness and shortness of breath. Treatment focuses on clearing phlegm and using antibiotics for infections.

Cystic fibrosis, a genetic disorder affecting the lungs and digestive system, stimulates the production of thick, sticky mucus. This mucus blocks airways, causing recurrent lung infections and a chronic, phlegm-producing cough. The phlegm may be yellow or green due to bacterial growth in the lungs. While incurable, treatment aims to manage symptoms and improve quality of life.

A persistent cough with blood-tinged phlegm can be a warning sign of lung cancer. However, lung cancer often has no obvious symptoms in its early stages. Early detection and timely intervention improve treatment outcomes.

Tuberculosis, a bacterial infection caused by Mycobacterium tuberculosis, primarily affects the lungs, causing a persistent, phlegm-producing cough, sometimes with blood. Other symptoms include persistent fever, night sweats, weight loss, and fatigue. Tuberculosis is contagious and requires prolonged antibiotic treatment to control the disease and prevent its spread.

Besides these conditions, a phlegm-producing cough can also stem from environmental factors and lifestyle habits such as smoking, exposure to smoke, dust, industrial chemicals, exhaust fumes, pollutants, pollen, animal dander, and mold. Unlike infections, allergy-related coughs are not usually accompanied by fever or body aches. Gastroesophageal reflux disease (GERD) causes stomach acid to flow back into the esophagus, irritating the throat and causing a chronic cough.

For accurate diagnosis, doctors may recommend chest X-rays or CT scans, sputum tests, pulmonary function tests (PFTs), bronchoscopy, blood tests, allergy tests to identify respiratory irritants, and esophageal pH monitoring if GERD is suspected. Treatment depends on the cause and may involve medication, lifestyle adjustments, increased fluid intake, and steam inhalation.

Thao Nhi