Coughing Up Phlegm (Mucus, Sputum from the Chest)

Meaning of Phlegm

Phlegm is the mucus expelled from the airways during coughing. It is also known as sputum. Normally the lining of the respiratory passages produces moderate amounts of mucus to help moisturize these linings and to trap dust and microbes. The movement of air through the respiratory passages has a drying effect and without mucus the lining of these passages would not be able to stay moist and supple. The added benefit is that by trapping dust and microbes in the air, this mucus can then be pushed out from the respiratory passages thereby preventing these foreign particles from reaching the deeper areas of the lung and possibly causes damage or disease.

Despite the normal presence of mucus, it does not full explain the reason for phlegm and sputum when coughing. For most healthy people, coughing does not cause the expulsion of mucus. However, when there is copious amounts of mucus then it can be coughed up as phlegm or sputum. Excessive mucus is seen in various inflammatory diseases, be it due to trauma, allergy or infection. Therefore the presence of phlegm or sputum means that the air passages are irritated or inflamed. Phlegm is actually not mucus only. It is more correctly a mixture of mucus and saliva.

Color of Phlegm

Due to the wide range of causes of coughing up of phlegm, it is important to take note of concomitant signs and symptoms to reach a differential diagnosis. This is a list of possible causes of the symptoms. Further diagnostic investigation can then confirm or exclude these diseases. One such important feature that should be noted is the color of phlegm. Mucus is usually slightly clear to whitish in color. However, when phlegm is of a different color, the hue may indicate the possible cause of the underlying condition.

It is important to note that trying to diagnose the underlying condition solely by the color of the mucus is not accurate. Modern diagnostic investigations coupled with clinical assessment is necessary and therefore the diagnosis should be left to a medical doctor.

Clear Phlegm

Coughing up clear phlegm is probably the least concerning. Phlegm is naturally slightly white in color. However, when there is excessive production of mucus it may be clearer in hue. Furthermore it may be mixed with copious amounts of saliva with saliva being naturally clear in color.  Clear phlegm grossly indicates that blood or pus is not present in the mucus. However, this should not be misleading because clear mucus could still be indicative of a serious underlying disease of the airways.

Yellow Phlegm

The presence of yellow phlegm is indicative of pus. This means that the inflammation of the air passages is due to an infection. Coughing up yellow to yellowish brown phlegm is common in most acute respiratory conditions. It is actually the presence of certain immune cells, the white blood cells such as neutrophils and eosinophils, that phlegm may take on a yellow color. While allergic conditions are more likely to lead to the coughing up of thick white phlegm, it may also contribute to yellow phlegm.

Green Phlegm

Coughing up green phlegm indicates a long standing infection. It may also be seen in chronic inflammatory diseases of the respiratory system. Green phlegm arises when a type of immune cell known as neutrophil degrades. Neutrophils are seen in abundance with chronic inflammation, be it due to infection or non-infectious causes. The release of an enzyme known as myeloperioxidase from the neutrophil breakdown accounts for the green color of phlegm.

Red Phlegm

Pink to red phlegm should always be considered to be due to the presence of blood in the mucus unless proved otherwise. Bleeding in the air passages or lungs is very serious and needs immediate medical investigation. It is known as hemoptysis. However, it is possible for red phlegm to be coughed up and not be associated with blood. Some bacteria may actually produce the red to rusty red pigment which stains the phlegm yet there is no blood present.

Blood can also cause phlegm to appear dark brown to black in color. When red blood cells degrade, a chemical known as hemosidern is released and this gradually changes the blood from a red color to a dark brown to black hue. However, just as with the red color, black phlegm can also be due to other causes like certain industrial dusts trapped in the mucus.

Causes of Coughing Up Phlegm

The causes of coughing up of phlegm is diverse. It is best assessed in the categories of diseases and conditions where coughing up phlegm is a symptom.


Infections of the respiratory passages is the most common cause of coughing up of phlegm. Most cases are acute and resolve without any complications.

  • Acute bronchitis is usually bacterial in nature and tends to develop after the common cold or flu. It is more frequently seen in cigarette smokers.
  • Pneumonia is an infection of the lung that can be caused by bacteria, viruses or fungi. It is often see in immune compromised people and with hospitalization.
  • Tuberculosis is a form of pneumonia caused by Mycobacterium tuberculosis. It is a very serious infection often seen in immune compromised states, and is frequently associated with malnutrition and HIV/AIDS.
  • Viral respiratory tract infections are common globally and are usually acute. Various viruses can infect the airways and lungs from the respiratory syncytial virus (RSV) in children to viral bronchitis and pneumonia in adulthood.


There are a wide range of non-infectious causes of respiratory tract and lung inflammation. Unlike with inflammation, these causes may not be related in mechanism although the symptoms like coughing up mucus are similar.

  • Asthma is a condition where airway hypersensitivity causes narrowing, swelling and excessive mucus production. It is commonly associated with allergies (allergic asthma) although non-allergic asthma can also occur.
  • Aspiration is where foreign bodies or substances enter the respiratory tract. It is often seen when the stomach contents enter the air passages causing severe chemical damage to the lining.
  • Chronic bronchitis is a chronic obstructive pulmonary disease (COPD) associated with prolonged cigarette smoking or occupational hazards.
  • Lung abscess is a collection of pus within the lung tissue. It may be related to an infection, aspiration or cancer.
  • Pneumoconiosis is a chronic lung disease that arises with the inhalation of organic or inorganic dusts. It is more commonly seen as an occupational hazard.
  • Lung cancer is a broad term that can refer to a malignancy of the lower airways, specifically the bronchi, or the lung tissue itself. It is more frequently seen among cigarette smokers and is one of the most common types of cancer.

Tests Conducted on Phlegm

The patient’s medical history, findings upon clinical examination be a medical doctor and possibly even the color of the phlegm may help to provide a possible differential diagnosis. However, lab tests are usually required for a definitive diagnosis. The main test in cases of coughing up mucus is a sputum cytology and culture.

  1. First the sputum sample has to be collected. The morning sputum is preferred.
  2. It is then examined under a microscope to identify the different cells and particles (cytology) and grow the microbes present within it (culture).
  3. The culture not only confirms the exact species of microorganism but can also help determine the sensitivity of these microbes to certain drugs. This is particularly useful in bacterial infections where antibiotic-sensitivity and possible resistance can be assessed before starting treatment.

Treatment for Phlegm

Coughing up phlegm is a symptom. It is not a disease on its own. Therefore there is no specific treatment for coughing up mucus. Instead different treatment measures have to be directed at the underlying cause.

  • Antibiotics for bacterial infections and antivirals for viral infections.
  • Corticosteroids for chronic inflammatory conditions including asthma.
  • Expectorants to assist with draining the mucus from the respiratory tract.

It is important to note that the quantity of phlegm will gradually ease as the underlying condition is treated appropriately. Eventually the coughing up of phlegm may resolve completely.

Draining Phlegm from the Chest

Coughing is very effective for draining phlegm from the respiratory passages and lungs. However, sometimes assistance is required and various techniques may be useful.

  • Moving around is helpful in ‘loosening up’ and expelling phlegm during coughing. Sitting and sleeping for long periods can hamper the expulsion of phlegm.
  • Chest physical therapy (“chest physio”) is also helpful in draining the phlegm. This involves :
    – postural drainage
    – percussion
    – deep breathing and coughing
  • A nebulizer is a device that delivers a vapor into the lungs. Medication can be added to the device for specific medical conditions.
  • Steam is also helpful in ‘loosening up’ the phlegm and assisting with expulsion of the phlegm during coughing.


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  1. Ramakrishna Verukonda February 5, 2017 at 1:12 am

    Which one is better for Phlgem decrement , is mucolytics by Nebulisation route or Oral route?
    Secondly , is Oral Expectorants or Oral Mucolytics ?

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