What Causes a Buildup of Mucus in the Lungs?

Reviewed on 3/9/2021

What is mucus in the lungs?

Mucus buildup in the lungs can be cased by infection, gastroesophageal reflux disease (GERD), smoking, cystic fibrosis, allergies, bronchiectasis, and chronic obstructive pulmonary disease (COPD).
Mucus buildup in the lungs can be cased by infection, gastroesophageal reflux disease (GERD), smoking, cystic fibrosis, allergies, bronchiectasis, and chronic obstructive pulmonary disease (COPD).

Mucus is a protective substance that’s created by many body parts such as the mouth, sinuses, throat, lungs, stomach, and intestines. About a liter of mucus is produced by your body every day. Its work is to keep internal organs moisturized and to trap bacteria that cause infections, and other unwanted substances like smoke and dust.

In the breathing system, mucus is referred to by two names. When it is in the nose, it is mucus. If it is in the lungs, then it’s phlegm or sputum. Your nose and lungs produce these important substances for themselves. While you may only notice mucus or phlegm when you are sick, they are always present and at work.

When too much of it ends up in your lungs, it can be a sign of a health problem. In some cases, your doctor will want to check you for lung diseases like bronchiectasis or chronic obstructive pulmonary disease. These conditions cause a buildup of mucus in the lungs and lead to coughing up of phlegm that may be thick and clear, or white in color. Sometimes it can be yellow, green, or black. All these could point to a problem in your lungs.

Symptoms of mucus in the lungs

Since mucus traps dirt and bacteria, having too much of it in the lungs is not healthy. A buildup of mucus begins to show with a cough that comes up with phlegm or sputum. A doctor would know what to check you for depending on the color of mucus you cough up, in addition to other signs and symptoms.

If you notice any of the following, it could be that there is too much phlegm in your lungs.


Wheezing or noisy breathing could be a sign that phlegm is blocking your lungs' airways or making them too narrow. Increased mucus in the lungs can block air passages, making it difficult for you to breathe in and out.

Chest congestion

Too much production of mucus in the lungs also causes a feeling of full lungs. A congested chest may also be a sign of a common cold or other infections.


When your lungs overproduce mucus, the natural way of getting rid of the excess is to cough it up. A cough may seem normal when it produces thick, clear, or white mucus. When there is a change in color, it could be a sign of infection.


COPD (chronic obstructive pulmonary disease) is the same as adult-onset asthma. See Answer

Causes of mucus in the lungs

There are several causes for the buildup of mucus in your lungs such as:


It is common to have excess mucus in your lungs when there is an infection such as cold, flu, or bacterial pneumonia.

Gastroesophageal reflux disease

If you have this condition, the acid in your stomach comes up the tube connecting your stomach, throat, and mouth. This can result in throat irritation and a feeling of mucus going down your throat (postnasal drip), along with chest congestion.


Scientists have found that cigarette smoking leads to overproduction of mucus in the lungs. A recent study reports that smoking pot even once a week causes more coughing and production of excess phlegm.


People who cannot tolerate substances like pollen or dust mites can experience chest tightness, congestion, and coughing. These symptoms may be accompanied by the accumulation of mucus in the chest. A person with seasonal allergies may find that staying hydrated helps to avoid congestion.

Cystic fibrosis (CF)

This condition causes mucus to become thick and sticky, which can clog the lungs and cause serious problems. CF is a chronic (long-lasting) and progressive (worsens over time) condition.


This is a disease of the lungs that causes a person to cough up yellow or green mucus almost every day. Although symptoms may take months or years to develop, a close examination by a doctor as soon as persistent cough with colored (sometimes bloody) sputum develops will help.

Chronic obstructive pulmonary disease (COPD)

COPD is a group of lung diseases that causes a buildup of thick and sticky mucus in your body’s organs like your lungs and pancreas. Symptoms include shortness of breath, wheezing, or a persistent cough. Consult your doctor if you experience a long-lasting cough that may produce mucus that may be clear, white, yellow, or greenish. Smoking is the main cause of COPD and is thought to be responsible for around nine in every ten cases.

When to see the doctor for mucus in the lungs

If you smoke or used to and experience any of the symptoms of the conditions mentioned above, consult your doctor. It is not wise to ignore the symptoms of a condition like COPD as it can significantly damage your lungs. Starting treatment as early as possible is important to maintain a healthy respiratory system. Also, coughing up colored mucus other than white or visibly clear means you should seek medical attention.

Diagnosis of mucus in the lungs

Once you visit your doctor about the situation, they will ask about your symptoms and whether you smoke or have smoked in the past. Like with many lung diseases, your doctor will listen to your lungs to check for blockages. This is done by conducting a breathing test that measures substances in your breath.

You might also hear your doctor mention a sputum culture. This is a test that checks for bacteria or another type of organism that may be causing an infection in your lungs or the airways leading to your lungs. You will be asked to breathe deeply and then cough deeply into a special cup.

If you can't, your doctor may consider performing bronchoscopy, which involves inserting a thin, light tube through your mouth or nose and into the airways. This procedure requires that you be put under special medication to distract you from discomfort or pain.


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Treatment of mucus in the lungs

There are many ways to reduce excessive mucus build-up in the lungs. In addition to using certain medicines to control coughing, shortness of breath, and other symptoms, your doctor may recommend chest physiotherapy or a group of physical techniques that improve lung function and help you breathe better.

Other interventions include airway clearance technique (ACT), a procedure that your doctor will help you understand. It includes practices such as postural drainage, mostly used in people who have cystic fibrosis to help them cough up mucus. Ask your doctor how you can use this and more airway clearance techniques to get rid of excess mucus in the lungs.

Your doctor may also ask you not to suppress a cough. Coughing is the body’s way of keeping excess mucus and other substances out of your lungs and throat. Upon checking your situation, the doctor can recommend that you use cough syrup.

Not only can these treatment options help reduce symptoms related to mucus production, but they can help you avoid infections such as bacterial pneumonia.

Health Solutions From Our Sponsors

American Academy of Allergy, Asthma & Immunology: "GASTROESOPHAGEAL REFLUX DISEASE (GERD)."

American Lung Association: "Warning Signs of Lung Disease."

Cystic Fibrosis Foundation: "About Cystic Fibrosis."

International Journal of Environmental Research and Public Health: "Smoking and Chronic Premier Health: Mucus and Phlegm: Barometers of Your Health."

MedlinePlus: "Sputum Culture."

MedPage Today: "Cigarette Smoke Ups Mucus in Lungs."

Michigan Medicine: "Cystic Fibrosis: Helping Your Child Cough Up Mucus."

National Heart, Lung, and Blood Institute: "Bronchiectasis."

National Health Service: "Causes-Chronic obstructive pulmonary disease (COPD)."

Obstructive Pulmonary Disease (COPD). "Parallel Epidemics of the 21st Century."

Science in the News: "All About That Mucus: How it keeps us healthy."

Wexner Medical Center: "What does the color of phlegm mean?"

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