What Is Sputum?

Sputum is a combination of mucus coughed up from the respiratory tract and saliva. It is usually a result of diseases or infections. Phlegm and sputum are often interchangeably used. Sometimes, the term mucus is used when referring to sputum or phlegm. However, mucus is also produced in the urogenital tract and gastrointestinal tract, making it a vague term to use when talking about respiratory secretions. 

Sputum is coughed up from the lower respiratory tract (trachea, bronchi, bronchioles, and alveoli) instead of coming from the throat and mouth. 

Sputum Color and What It Indicates

The consistency and color of sputum can help identify different respiratory conditions. Sputum may contain cellular debris, blood components, microorganisms, immune cells, and dust. The color of sputum usually depends on the quantity of these components and the type of respiratory disease or infection, which is why sputum may show a variety of colors and consistency. 

1. Clear Sputum

Each day, the body produces clear mucus filled with protein, water, dissolved salts, and antibodies to help lubricate the respiratory system. When the body produces increased amounts of clear phlegm, it may indicate that the body is flushing out irritants such as viruses or pollen. Although clear sputum is often normal, certain lung diseases may increase its amount. Below is a list of common causes of clear sputum:

• Allergic Rhinitis: Also commonly called as hay fever or nasal allergy, it is a condition in which the body produces an increased amount of nasal mucus following allergen exposure. Examples of allergens are weeds, pollen, and grasses, which make people cough up clear sputum as well as cause postnasal drip. 

• Viral Pneumonia: This type of lung infection also causes increased production of clear sputum along with symptoms such as a dry cough, fever, and other flu-like symptoms.

• Viral Bronchitis: This lung condition is characterized by bronchial tube inflammation, which often starts with coughing up white or clear sputum. In some people with viral bronchitis, their sputum progresses and changes into yellow or green in color. 

2. White Sputum

This sputum color may be caused by several health conditions, which include:

• Chronic Obstructive Pulmonary Disease (COPD): This chronic lung disease causes an excessive mucus production along with inflammation and narrowing of the airways. People with COPD usually have a hard time getting oxygen into their body. 

• Viral Bronchitis: Although this lung condition starts with the production of white sputum, it may turn into green or yellow if the condition develops into a bacterial infection. 

• Congestive Heart Failure: This heart condition occurs when the heart does not pump enough blood all throughout the body. In this condition, shortness of breath is experienced along with fluid buildup in the different areas, which leads to edema. The fluid accumulated in the lungs may cause an increased production of white sputum. 

• Gastroesophageal Reflux Disease (GERD): GERD is a chronic condition that occurs when stomach acid travels from the stomach up to the esophagus. People with this digestive disorder may cough up white sputum.

If you are experiencing breathing difficulties, seek medical help right away. 

3. Yellow or Green Sputum

Lower respiratory tract infections such as pneumonia can cause the production of yellow to green-colored sputum. When neutrophils, a type of white blood cells, fight off infection, they impart a green color in the mucus. In such cases, bacterial infection is suspected, which may need antibiotic treatment. 

4. Brown Sputum

Brown sputum may also show a rusty appearance, after having pink or red phlegm. The brown color of sputum often signifies old blood. It may also be caused by the presence of tar, which can be found in people who smoke.

The common causes of brown sputum are:

• Cystic Fibrosis: This inherited lung disorder may produce a rust-colored sputum.

• Bacterial Bronchitis: As this lung condition progresses, brown-colored sputum may be produced. People who have chronic bronchitis, including people who smoke or are frequently exposed to irritants or fumes, may also cough up brown sputum. 

• Bacterial Pneumonia: This type of pneumonia can also cause rust-colored or greenish brown sputum. 

• Lung Abscess: It is a pus-filled cavity within the lungs. It is often surrounded by inflamed and infected lung tissue. Its most common symptom is a productive cough that brings up a foul-smelling, blood-streaked or brown-colored sputum. Other symptoms include loss of appetite and night sweats. 

• Pneumoconiosis: It is a lung disease caused by inhaling dust, such as asbestos, coal, and crystalline silica. This occupational lung disease is incurable and causes the production of brown sputum. 

5. Pink or Red Sputum

Coughing up pink or red sputum may indicate the presence of blood. Pink or red sputum is often caused by the following conditions:

• Pneumonia
• Tuberculosis
• Congestive heart failure (CHF)
• Lung cancer

Sputum production can also be increased by the following factors:

• Smoking: Mucus builds up in the lungs of smokers and often leads to the development of a smoker's cough. In such cases, the sputum may appear bloody, green, or yellow in color.

• Asthma: The airways of people with asthma are sensitive to environmental pollution, allergens, and respiratory infections. The airways can become inflamed and can cause an excessive production of mucus.

Tests to Evaluate Sputum

The contents of sputum and anything else related to sputum can be analyzed in the laboratory. These tests may include:

• Sputum Culture: This test is performed to identify specific harmful microorganisms that infect the lungs. This test helps healthcare providers know the most effective antibiotic to give their patients if a bacterial strain is identified.  

• Sputum for Tuberculosis: A sputum sample is obtained for laboratory examination to determine if patients have tuberculosis.

• Sputum Cytology: This type of test involves the evaluation of sputum under the microscope to identify signs of cancer or tuberculosis. 

Decreasing Sputum Production

Numerous ways can be done to decrease the production of sputum. However, identifying the root cause of excessive sputum production should be done first. When it comes to smoking and air pollution, increased sputum production is normally expected since the body attempts to get rid of foreign matters that get inside the body. 

Certain medications such as expectorants and aerosol treatments may help reduce sputum production in such cases. However, the best approach would still be removing the irritants or the source of the problem. For some people, postural drainage may help. 

Bottom Line

Sputum consists of white blood cells, foreign matter, and a combination of cells. It is produced by the respiratory tract, and may vary in consistency, color, and amount. These characteristics can help healthcare providers diagnose a variety of medical conditions, which include tuberculosis and lung cancer. 

Although it can be quite annoying to experience an increased amount of sputum, know that it is the body's way to remove foreign matter that can cause damage to the airways.