What Causes a Buildup of Mucus in the Lungs?

Medically Reviewed on 4/7/2022

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.


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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.

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.

What is the best cough medicine for adults?

All cough medicines aren’t the same. The type of cough suppressant that may work best for you depends on the type of cough you have.

Here is how to choose the best cough medicine for your symptoms:

  • Nonproductive cough: This means dry cough or cough with no sputum or mucus production. A dry cough can be quite irritating and may keep you up at night. 
    • Medications to treat dry cough are called cough suppressants or antitussives. These medications suppress the cough reflex, thereby providing relief. 
    • Dextromethorphan is a popular cough suppressant available in various forms including lozenges, syrups, and tablets.
      • It can cause certain side effects such as drowsiness, shakiness, dizzinessblurred vision, and confusion. Thus, be careful while using this medication.
      • You may want to avoid activities such as driving while you are taking dextromethorphan.
      • Because of its potential for drug abuse due to its hallucinogenic effect (also called robotripping), some states have limited the quantity of dextromethorphan in people older than 18 years. However, currently, there is no federal ban or restriction on this drug.
  • Productive cough: It is also called wet cough because it is associated with the production of mucus or sputum along with cough.
    • Using a cough suppressant for wet cough may worsen the condition by preventing the expectoration (coughing out) of excessive mucus from your lungs.
    • Suitable medications, in this case, are called cough expectorants that help loosen up and remove the irritating mucus from your respiratory tract and provide relief.
      • Guaifenesin is the ingredient used in expectorant cough formulations. 
      • Some cough formulations may contain potassium iodide that helps loosen the mucus by making it more watery.

Besides the above two groups of cough medications, over-the-counter formulations may contain other ingredients such as nonsteroidal anti-inflammatory drugs (NSAIDs) or antihistamines.

  • NSAIDs help relieve symptoms such as fever and pain, whereas antihistamines help relieve allergies.

Combination preparations must be avoided if you do not have additional symptoms with a cough. Such prescription may unnecessarily put you at risk of side effects from the ingredients that weren’t needed in the first place.

Non-medicated hard candies may help relieve cough and sore throat.

Several cough remedies are available over-the-counter (OTC); however, before you try any cough medications, make sure that you seek approval from your doctor, especially if you are pregnant, are lactating, or have any underlying health condition such as diabetes or kidney disease.

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Reasons not to suppress a cough

Coughing is your body’s reflex mechanism to get rid of harmful substances from your respiratory tract.

Suppressing coughing can at times do more harm than good by preventing the removal of irritating or harmful substances including bacteria and excess mucus from your body. Nonetheless, excessive coughing can perturb work, rest, and sleep and may even make you puke.

Home care for faster recovery from cough

You may get relief from cough by following these tips:

  • Take plenty of fluids including water, homemade vegetable and fruit juices, electrolyte solutions, warm soups, and broths.
  • Take enough rest.
  • Run a humidifier in your room.
  • Try steam inhalation.
  • If you have a stuffy nose, saline nasal drops may help relieve it.
  • Completely avoid smoking, including second-hand smoke.
  • Give honey and grated ginger in warm water to those older than five years.

When to contact your doctor

Contact your doctor if:

  • Your symptoms worsen.
  • Your cough does not go within a week.
  • You develop a high fever.
  • You have trouble breathing or chest pain.
  • You feel unusual lethargy or drowsiness.
  • You have wheezing or noisy breathing.
  • You have underlying health conditions such as diabetes, chronic lung conditions, high blood pressure, and glaucoma or are pregnant or breastfeeding.
  • You have developed symptoms after being in contact with an individual with COVID-19.

Owing to the ongoing flu and COVID-19 menace, it is always advisable to seek professional guidance for fever or any respiratory symptoms such as cough, difficulty breathing, or runny nose.

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Medically Reviewed on 4/7/2022
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American Lung Association: "Warning Signs of Lung Disease."

Cystic Fibrosis Foundation: "About Cystic Fibrosis."

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MedlinePlus: "Sputum Culture."

MedlinePlus: "Cold and Cough Medicines."

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."

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