Mucus vs. Phlegm: A Guide to Clearing Up the Confusion

Man's hand grabbing tissue paper from box on wooden table with blur natural mountain view background.

Mucus and phlegm are natural substances our bodies produce to help protect and lubricate the respiratory system. But are they the same thing? Phlegm is indeed a type of mucus, but its presence, color, and consistency can tell you a lot about your lung health.

Uncovering the Difference between Mucus and Phlegm

A simple way to think about the relationship between mucus vs. phlegm is this:

  • Mucus provides a protective layer¹ for the respiratory system, trapping dust, bacteria, and other particles before they can enter the lungs.  
  • Phlegm is mucus your body produces in the lungs and throat,² which you then try to cough up to clear irritants and infections from the lungs.

Both work to support our immune system, yet each has its unique purpose. This article explains the difference between mucus and phlegm and how to manage symptoms for better airway clearance.

First, let’s review the basics.

What Is Mucus?

Mucus is a slippery, gel-like fluid that is produced in different areas of the body, including your nose and sinuses.³ 

As mentioned, it’s a natural response to various irritants, such as allergens, viruses, bacteria, and pollutants.4 However, our bodies are constantly producing mucus to support vital functions. For example, mucus helps lubricate and protect the respiratory system by keeping the airways moist and preventing dryness. 

Mucus is typically clear or white in color but can become thicker or more abundant (i.e., excessive mucus) if you’re experiencing the flu, allergies, or an underlying lung condition.

This brings us to phlegm.

What Is Phlegm?

Phlegm, also called sputum, is a type of mucus we produce in the respiratory system, specifically in the lungs and throat.5 It’s often described as thicker and stickier than regular mucus, making it difficult to breathe.

You may experience phlegm production due to an irritation in the respiratory system that’s causing inflammation in the airway tissue.6 

Common irritants include allergens, such as: 

Graphic banner to show common irritants.

  • Pollen
  • Dust
  • Air pollution and irritants 
  • Cigarette smoke7 

Infections like colds and the flu can also trigger increased phlegm production as the body tries to fight it. In some cases, certain chronic lung conditions like asthma, chronic obstructive pulmonary disease (COPD), and bronchiectasis can also lead to increased phlegm production due to the repeated cycles of inflammation and infections.8

Like mucus, phlegm is usually clear or white; however, changes in the color or consistency of phlegm can be a sign of a more severe condition.

Different Colors of Phlegm

The color of your phlegm may provide important clues about your health, including whether or not an underlying lung condition is causing a change in normal mucus production.

Below, we’ve included brief descriptions of the different colors of phlegm and what they mean:9

Clear and white color comparison.

Clear or white phlegm

Clear or white phlegm is considered normal and healthy. It’s usually a sign that your respiratory system is functioning properly and is not infected or inflamed. 

However, if you notice an increase in clear or white phlegm, it may be a sign of allergies or a viral infection. 

Yellow and green color comparison.

Yellow or green phlegm

Yellow or green phlegm can indicate an infection, such as a cold or flu. The color comes from your white blood cells fighting off the infection. 

In some cases, yellow or green phlegm can also signify a more serious bacterial infection.

Brown and black color comparison.

Brown or black phlegm

Brown or black phlegm can be a sign of different health issues. In some cases, it may be due to smoking, a fungal infection, or bronchitis.10

Red and pink color comparison.

Red or pink phlegm

Red or pink phlegm can indicate bleeding in the respiratory tract, which may be caused by various factors, including infections, inflammation, or more serious lung diseases.10

If you are experiencing changes in the color of  your phlegm, you’ll want to contact your healthcare team to discuss this and any other accompanying symptoms that may include fever, chronic cough, fatigue, etc.

Two SmartVest users sitting on cough talking.

Finding Relief with Airway Clearance

Some people may experience excessive mucus production due to underlying conditions like bronchiectasis. In this case, treatment is necessary to help manage symptoms and keep the lungs more clear.

Airway clearance techniques offer effective ways to prevent mucus buildup in the lungs. By using a combination of high-frequency chest wall oscillation (HFCWO) therapy, breathing exercises, and huff cough, individuals can clear out excess mucus and debris that can accumulate in the airways, so you can breathe easier.

With the SmartVest Airway Clearance System, regularly performing airway clearance can stabilize lung function, reduce hospitalization, and decrease antibiotic usage to treat infections.11 

Say Goodbye to Mucus Buildup!

If you’re living with bronchiectasis and struggling with mucus buildup, talk to your clinician about SmartVest and if it could be a good option for you.

To get started, request an informational packet to be mailed to your home. Inside, you’ll find more information on how SmartVest works, clinical research on its effectiveness, and real-life testimonials of satisfied SmartVest users.

Additionally, we’ve included a prescription form to bring to your next doctor’s appointment so that you can experience relief from your symptoms.

In the meantime, we’re here to help if you have questions! Schedule a chat with one of our Patient Care Advocates, who are also Respiratory Therapists, to get the information you need to feel confident and take the next step in your journey to airway clearance!

Want to chat? Connect with us! Talk to our respiratory therapists.


[1] Medical News Today. “19 Home Remedies for Phlegm and Mucus.” Retrieved from

[2] Cleveland Clinic. “Coughing Up Phlegm.” Retrieved from

[3] Medical News Today. “Mucus: Where Does It Come From and How Is It Form?” Retrieved from

[4] Medical News Today. “Mucus: Where Does It Come From and How Is It Form?” Retrieved from

[5] American Lung Association. “Understanding Mucus in the Lungs.” Retrieved from

[6] Medical News Today. “Mucus: Where Does It Come From and How Is It Form?” Retrieved from

[7] Cleveland Clinic. “Coughing Up Phlegm.” Retrieved from

[8] Cleveland Clinic. “Coughing Up Phlegm.” Retrieved from

[9] Medical News Today. “What Is Sputum (Phlegm) Tell Us.” Retrieved from

[10] Medical News Today. “What does green, yellow, or brown phlegm mean?” Retrieved from

[11] Powner J, Nesmith A, Kirkpatrick DP, Nichols JK, Bermingham B, Solomon GM. Employment of an algorithm of care including chest physiotherapy results in reduced hospitalizations and stability of lung function in bronchiectasis. BMC Pulm Med. 2019;19(1):82. Published 2019 Apr 25