Phlegm and mucus, although related, are not exactly the same. Phlegm is usually found in the back of the throat or in the lungs, and originates from the lower respiratory tract. On the other hand, mucus is usually found on the nasal mucosa and acts as a protective filter for the lungs during inhalation. You can easily remove mucus by blowing your nose. In contrast, the phlegm in the throat is thick and sticky, and is often observed when coughing. Excess phlegm can indicate respiratory diseases such as bronchitis.

Mucus composition:

Our bodies naturally produce mucus and phlegm as protective, slippery substances that form in the throat, sinuses, and lungs. It helps protect the body’s cells and traps irritants and bacteria. If bacteria or viruses overcome your body’s natural defenses, more phlegm will be produced. In most cases, excess mucus and phlegm will resolve on their own. However, in some cases, excess mucus can accumulate in the bronchi, making the lungs vulnerable to infection, as seen in conditions such as bronchiectasis and cystic fibrosis. When you cough, your body tries to get rid of this substance.