Chronic Postnasal Drip: This condition, often due to allergies or a deviated septum, leads to the constant dripping of mucus from the back of the nose into the throat, causing a sensation of chronic phlegm.

Gastroesophageal Reflux Disease (GERD): Stomach acid flowing back into the esophagus can irritate the throat, leading to increased mucus production and the sensation of phlegm.
Chronic Bronchitis: A type of COPD, chronic bronchitis involves inflammation of the bronchial tubes, leading to a persistent cough and mucus production.
Allergic Rhinitis: Allergies can cause nasal congestion and increased mucus production, which can lead to a sensation of phlegm in the throat.
Sinusitis: Inflammation or infection of the sinuses can cause increased mucus production, which may drain into the throat.

Lung Cancer: Although less common, lung cancer can cause chronic cough and mucus production. It's crucial to rule out this potentially life-threatening condition.
Tuberculosis (TB): A bacterial infection that primarily affects the lungs, TB can cause chronic cough, mucus production, and other systemic symptoms.
Pneumonia: Especially in vulnerable populations, pneumonia can present with chronic cough and phlegm production.

Cystic Fibrosis: A genetic disorder that leads to the production of thick, sticky mucus, which can cause respiratory and digestive problems.
Primary Ciliary Dyskinesia: A rare genetic disorder affecting the cilia in the respiratory tract, leading to chronic respiratory infections and mucus accumulation.
Vocal Cord Dysfunction: Abnormal movement of the vocal cords can cause symptoms similar to asthma, including chronic cough and sensation of phlegm.