Clear, bubbly phlegm does not typically indicate a problem. However, coughing up large amounts could indicate an underlying health issue, such as fluid in the lungs.

Phlegm, or sputum, is a type of mucus that the respiratory tract produces. The color of phlegm can help identify certain health issues, such as infections or problems affecting the lungs.

This article looks at what clear, bubbly phlegm may mean, other colors of phlegm, and when to contact a doctor.

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Clear phlegm is usually not a cause for concern. However, if someone produces large amounts of clear, frothy, or bubbly phlegm, it may indicate a health condition.

Fluid in the lungs

Clear, bubbly phlegm may be a sign of pulmonary edema, or fluid in the lungs.

It is important to monitor this condition, particularly if people have swollen hands and feet or if they take diuretics.

Bronchiectasis

Bronchiectasis is a widening of the airways in the lungs, which leads to a buildup of mucus.

One of the most common symptoms of bronchiectasis is coughing up large amounts of clear, pale yellow, or yellow-green phlegm.

The phlegm may contain pus mixed into the fluid, which may give it a bubbly appearance.

GERD

Gastroesophageal reflux disease (GERD) is chronic acid reflux, in which the stomach contents flow back up into the esophagus.

GERD is a risk factor for phlegm production. A symptom of GERD may include coughing up bubbly phlegm. Other symptoms include:

Phlegm can come in various colors, which can indicate if an infection or health problem is present.

Phlegm color may also help identify if a health issue is getting better and help determine the best course of treatment.

Yellow or green

Yellow or green mucus tends to indicate an infection. For example, people with pneumonia, a lung infection, may have a cough that produces green or yellow phlegm.

Yellow-green phlegm is also a potential symptom of cystic fibrosis. Cystic fibrosis causes a buildup of mucus in the lungs and digestive system.

Brown

Brown phlegm may occur due to old blood in the mucus. This may occur due to lung diseases such as:

  • cystic fibrosis
  • pneumonia
  • bronchitis

Inhaling brown substances, such as dust or toxins, may also cause brown-colored phlegm.

Red

Red phlegm, or blood in phlegm, can occur due to:

Coughing up blood may be a sign of a pulmonary embolism. A pulmonary embolism is a blood clot that breaks loose and travels to the lungs, which can be life threatening.

Black

Black mucus, or melanoptysis, may occur due to:

Black phlegm may occur due to inhaling certain substances. Black phlegm can be a symptom of coal worker’s pneumoconiosis (CWP), or black lung disease.

CWP occurs due to the inhalation of coal dust and is most common in coal miners.

People can contact a doctor if they have any concerns about the color, texture, or amount of phlegm they are producing.

Any unusual changes to phlegm may indicate an issue. It may help to track and record when coughing up phlegm starts and how long it continues.

If phlegm continues for more than a few weeks, or if other symptoms are present, it is a good idea to contact a doctor. People may also benefit from contacting a doctor if they have yellow-green, red, pink, or dark-colored phlegm.

People will need to seek immediate help if they are coughing up blood and have symptoms of pulmonary embolism, such as:

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Phlegm with COPD may be clear, but people may cough up large amounts.

During acute exacerbations of COPD, which are sudden worsening of symptoms, phlegm may increase and change from clear or whitish to green or yellow. This could indicate a bacterial infection.

Coughing up clear jelly balls may be due to catarrh, a buildup of mucus in the airways. This may occur due to allergies, infections such as colds or flu, pollution, or nasal polyps.

If symptoms continue for more than a few weeks, it is a good idea to contact a doctor to find out the cause and get treatment.

Clear, bubbly phlegm may not be a sign of a problem, but large quantities may indicate a health issue.

If people notice any unusual changes in the amount, texture, or color of phlegm, they should speak with a doctor.

People may benefit from contacting a doctor if they have persistent green-yellow phlegm or blood in the phlegm.