Phlegm Versus Mucus: What’s The Difference?

Even when you do not realize it, your body works behind the scenes 24/7 to keep you functioning. Mucus is one such silent partner invested in your well-being.

Every day, the body’s mucous membranes secrete 1 to 1.5 liters of a clear, stringy fluid called mucus, most of which we never feel when we swallow.

People with chronic obstructive pulmonary disease (COPD) or other chronic lung conditions often make and expel an oversupply of mucus and phlegm due to an increased number of mucous-producing cells and over-sized mucous glands in the airways.

After swallowing, the fluid left behind keeps airways and other essential organs well-hydrated. Mucus also functions as a protective filter.

Just like an air filter that traps dirt, debris, dust and smoke moving through the air in a house, mucus traps the same foreign substances and bacteria moving through the air in the body.  

3 Differences Between Phlegm and Mucus

In addition to “mucus,” you may also hear the word “phlegm.” Although the terms are used interchangeably, there are a few differences between them:

  1. Mucus is a clear, stringy fluid produced by mucous glands in tissues lining the nose, mouth and throat.  
  2. Phlegm is a form of mucus produced by the lungs and lower respiratory tract. Phlegm indicates the presence of inflammation and irritation in the lungs and airways.
  3. Mucus is more often expelled from the nose, while phlegm is expelled from the lungs via coughing.  

The Phlegm and Mucus Cycle

The process of removing mucus and phlegm can become a vicious cycle if you are suffering from COPD:

  • Chronic lung disease causes airway inflammation, which spurs the production of phlegm in the respiratory tract.
  • This phlegm gets caught in the airways and makes breathing difficult, especially for lungs that are already working harder than normal to breathe.
  • The body uses coughing as a natural mechanism to remove excess mucus and phlegm. However, coughing irritates airway tissues even further and causes production of more phlegm in the lungs.
  • Over time, chronic mucus production that builds up in the respiratory tract can lead to a decline in lung function.   

Changes in Mucus

Respiratory infections, sinus infections, bacterial infections, allergies, smoking and environmental toxins can trigger changes in the amount of mucus your body makes, as well as its color.

If you have increased coughing and removal of mucus that is thick or discolored, you may be developing an infection or experiencing a COPD flare-up.  

If you have a chronic lung disease, it is important that to keep your nose, throat, lungs and airways as clear of mucus and phlegm as possible.

Infections and airway obstruction resulting from excess mucus and phlegm can increase your risk of exacerbations, hospitalizations and progression of a chronic lung condition.