Main causes of phlegm
Infections: Viral and bacterial infections such as colds, flu, bronchitis, sinusitis, or pneumonia increase the production of mucus in the lungs.
Allergies: Dust, pollen, pet dander, or other allergens in the air cause allergies in the airways and cause mucus production.
Air pollution: Vehicle exhaust, pollution from factories, and dust from construction sites irritate the lungs and cause mucus to build up.
Smoking: Smoking interferes with the natural cleansing ability of the lungs. This causes mucus to build up and lead to chronic cough.
Asthma: Swelling in the airways in people with asthma can cause mucus to build up.
Dry environment: If the humidity in the air is too low, the lungs feel dry and the body produces more mucus as a defense mechanism.
Dietary habits: Some people find cold foods, ice cream, and excessive sweets to be phlegmy (this can vary from person to person).
