Phlegm, also known as sputum, is a thick secretion from the airways. It's thicker and comes from deeper in the respiratory tract than the thin secretions you may experience with a simple runny nose. Coughing up phlegm, known as a productive cough, is commonly due to viral respiratory infections that the body may clear on its own, but sometimes it can signal a more serious problem.

Read on if you're coughing up phlegm and looking to learn about possible causes and treatments.

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What Causes Productive Cough?

Mucus is a normal part of the respiratory system that plays an important role in lubricating the airways and defending us against irritants and pathogens. However, inflammation from various causes results in an increase in mucus production and a thicker consistency. This results in the familiar symptoms of runny nose, congestion, and coughing up phlegm.

Respiratory infections are a common cause of inflammation resulting in a productive cough. Bronchitis and pneumonia are two types of infections that typically lead to a productive cough.

In bronchitis, the branches of the airways become inflamed and produce thicker mucus. In pneumonia, the lung tissue is infected. Respiratory infections can be due to viruses or bacteria. The cough is typically accompanied by other symptoms, like fever, chills, sore throat, muscle aches, fatigue, and a general ill feeling.

Possible Causes Unrelated to Infection

While infection is a common cause, there are several noninfectious causes of phlegm production. These include:

Some environmental and lifestyle factors can also increase phlegm. These include:

  • Smoking
  • Exposure to air pollution
  • Alcohol use

What Does the Color of Phlegm Mean?

While diagnosing the cause of a productive cough does not rely on phlegm color, it can suggest certain causes. Normally, mucus is clear, but phlegm can come in a range of colors that may point to the underlying cause:

  • Clear or white phlegm may be seen with allergies, viral infection, underlying lung disease, GERD, and heart failure.
  • Green phlegm may be seen with a bacterial infection.
  • Pink phlegm suggests fluid in the lungs, known as pulmonary edema, such as in heart failure.
  • Red phlegm indicates the presence of blood and may be seen with lung cancer or pulmonary embolism.
  • Black phlegm can occur with pollutant exposure, such as from cigarette smoke or air pollution, smoke from fire, or fungal infection.


Treating a productive cough depends on the underlying cause. Medications and supportive care at home can help treat a productive cough.


Treating the underlying cause of productive cough may include medications, some of which require a prescription from a healthcare provider. These include:

The Issue With Antibiotics

If you are coughing up phlegm and have symptoms of infection, like fever, chills, and fatigue, you might expect to receive antibiotics to treat it. But if your healthcare provider recommends a trial of supportive care instead of antibiotics, know that it's for a good reason. Most infectious causes of cough are due to viruses and not bacteria. Antibiotics treat bacterial infections, so they won't necessarily be effective in the case of a viral infection. Viral infections, like the common cold, will often be cleared by the body on their own and do not require specific medical treatment beyond supportive care at home. Importantly, antibiotics can have significant side effects, and overuse of antibiotics contributes to antibiotic resistance.

How to Encourage Coughing Up Phlegm at Home

Supportive treatment for productive cough includes measures to encourage coughing up the phlegm. This can help rid the body of phlegm and underlying irritants.

The following measures can help your body get rid of phlegm:

  • Drink plenty of fluids
  • Use a humidifier
  • Take a hot shower
  • Try a teaspoon of honey
  • Use over-the-counter (OTC) medications (like guaifenesin and bromhexine) such as expectorants and mucolytics that loosen mucus to make it easier to cough up

When to See a Healthcare Provider

if your cough isn't getting better after 10 days, it's time to discuss your symptoms with your healthcare provider. Other concerning symptoms should be reported to your healthcare provider for further investigation. These include:

  • Difficulty breathing
  • Fever, especially if lasting more than four days
  • Weight loss
  • Coughing up blood
  • Signs of heart failure, such as swollen legs and difficulty breathing when laying flat


Phlegm is a thick mucus from the lower airways due to lung inflammation or injury. Infection is a common cause, but other conditions like allergies, lung disease, and GERD can cause a productive cough. Treatment depends on the underlying cause and includes supportive care and medications. Your healthcare provider can help determine the underlying cause and recommend a treatment plan if you are experiencing this unpleasant symptom.

By Angela Ryan Lee, MD

Angela Ryan Lee, MD, is board-certified in cardiovascular diseases and internal medicine. She is a fellow of the American College of Cardiology and holds board certifications from the American Society of Nuclear Cardiology and the National Board of Echocardiography. She completed undergraduate studies at the University of Virginia with a B.S. in Biology, medical school at Jefferson Medical College, and internal medicine residency and cardiovascular diseases fellowship at the George Washington University Hospital. Her professional interests include preventive cardiology, medical journalism, and health policy.

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