Where Does Phlegm Come from?

Phlegm is a slightly different substance. It's a form of mucus produced by the lower airways — not by the nose and sinuses — in response to inflammation. You may not notice phlegm unless you cough it up as a symptom of bronchitis or pneumonia.

What is the main cause of phlegm?

Respiratory infections like colds, the flu, and sinusitis are common causes of increased mucus production and coughing up mucus. Allergic reactions are another reason that mucus production can increase. Even consumption of spicy foods can spark excess mucus production in the nasal passages.

Where does phlegm build up?

Phlegm is a type of mucus produced in the lungs and lower respiratory tract. It is most noticeable when a person is acutely sick or has a longstanding health condition.