Phlegm Definition, Colors, Causes, and Conditions Vector

Phlegm: Definition, Colors, Causes, and Conditions (2024)

by | Updated: Apr 21, 2024

Phlegm is a viscous, gel-like substance produced by the respiratory system as a response to infections, allergies, or irritants.

It serves as a crucial defense mechanism, trapping foreign particles and pathogens to prevent them from entering deeper into the lungs.

The color, consistency, and quantity of phlegm can provide valuable insights into the underlying causes and conditions affecting the respiratory system.

What is Phlegm?

Phlegm is a thick, sticky mucus produced by the respiratory system, primarily during illness. It serves as a defense mechanism, trapping pathogens and irritants, and aiding in their removal from the body. Phlegm’s color and consistency can vary, providing clues about one’s health and the nature of their respiratory issues.

Phlegm color chart illustration


Phlegm can appear in various colors, each indicating different health conditions:

  • Clear: Healthy, indicating normal respiratory health.
  • White: Can signify mild respiratory infections, congestion, or conditions like chronic bronchitis.
  • Yellow or Green: Often a sign of a bacterial or viral infection. The color comes from the presence of white blood cells.
  • Red or Pink: Suggests the presence of blood, potentially due to bronchitis, pneumonia, or even lung cancer.
  • Brown or Black: May be caused by the inhalation of substances like tobacco smoke or pollution, or it could indicate a fungal infection or more severe lung conditions.

Note: Changes in phlegm color can provide clues to underlying health issues, but should be interpreted within the broader context of other symptoms and a medical assessment for accurate diagnosis and treatment.

Clinical Significance

The clinical significance of phlegm lies in its ability to provide valuable insights into the health of the respiratory system and the body’s response to various conditions.

Phlegm production is a common symptom in many respiratory diseases and infections, serving both as a protective mechanism and as a potential diagnostic tool.

Here are some key points regarding the clinical significance of phlegm:

  • Indicator of Infection or Inflammation: The presence, quantity, and quality of phlegm can indicate the presence of an infection or inflammation in the respiratory system. For instance, clear phlegm is often associated with viral infections, while green or yellow phlegm can indicate a bacterial infection.
  • Disease Diagnosis: The characteristics of phlegm, such as color, consistency, and the presence of blood or other substances, can help healthcare providers diagnose specific respiratory conditions. For example, thick, green phlegm might suggest a bacterial infection such as bronchitis or pneumonia, whereas bloody phlegm could be a sign of a more serious condition like tuberculosis or lung cancer.
  • Monitoring Disease Progression and Treatment Response: Changes in phlegm production and characteristics can be used to monitor the progression of respiratory diseases and the response to treatment. A decrease in the amount of phlegm or a change from purulent (pus-like) to clear phlegm can indicate that the body is successfully fighting off the infection.
  • Complications of Excessive Phlegm Production: While phlegm production is a natural defense mechanism, excessive phlegm can lead to complications, including airway obstruction, increased risk of secondary infections, and impaired gas exchange. In chronic conditions like chronic obstructive pulmonary disease (COPD) or cystic fibrosis, managing phlegm production is a critical component of care to prevent exacerbations and maintain lung function.
  • Target for Therapeutic Interventions: Treatments may target phlegm production and clearance to alleviate symptoms and improve breathing. These can include expectorants (which thin the mucus), mucolytics (which break down the mucus), hydration, and physical therapy techniques to enhance mucus clearance from the respiratory tract.

Understanding the role and characteristics of phlegm is crucial for healthcare providers in diagnosing, monitoring, and treating respiratory conditions effectively.

It highlights the body’s efforts to protect and clear the respiratory tract, serving as a key indicator of health and disease states.

Where Does Phlegm Come From?

Phlegm comes from the respiratory system, specifically produced by the mucous membranes lining the airways, including the throat, bronchi, and lungs.

These membranes secrete mucus as a protective response to irritants, infections, or allergens.

Phlegm acts to trap foreign particles, bacteria, and viruses, aiding in their removal from the body, either through coughing it up or swallowing it to be neutralized by stomach acids.

Its production increases in response to respiratory infections or conditions, playing a crucial role in defending the respiratory system and maintaining lung health.

Disorders That Cause Phlegm

Several disorders can cause the production of excess phlegm, often as a response to infection, inflammation, or irritation of the respiratory tract.

Here are some of the common conditions associated with increased phlegm production:

  • Common Cold and Influenza: Viral infections like the common cold and flu can lead to increased production of clear or white phlegm as part of the body’s immune response to fight off the virus.
  • Bronchitis: Inflammation of the bronchial tubes, which carry air to and from the lungs, can result in the production of thick, discolored phlegm. Acute bronchitis is often caused by infections, while chronic bronchitis is usually due to long-term irritants like smoking.
  • Pneumonia: This infection inflames the air sacs in one or both lungs, which may fill with fluid or pus, leading to productive coughs with green, yellow, or even bloody phlegm.
  • Chronic Obstructive Pulmonary Disease (COPD): COPD, including chronic bronchitis and emphysema, is a chronic inflammatory lung disease that causes obstructed airflow from the lungs. Patients with COPD often produce a significant amount of mucus.
  • Asthma: While asthma is primarily known for causing difficulty breathing due to narrowed airways, it can also lead to the production of clear, thick phlegm, especially during an asthma attack.
  • Cystic Fibrosis: This genetic disorder leads to the production of abnormally thick and sticky mucus, which can obstruct the airways and lead to frequent lung infections, resulting in increased phlegm production.
  • Allergic Rhinitis: Commonly known as hay fever, allergic rhinitis can cause postnasal drip, leading to phlegm production as mucus drains from the sinuses into the throat.
  • Sinusitis: Infection or inflammation of the sinuses can lead to sinus congestion and postnasal drip, contributing to throat irritation and phlegm production.
  • Gastroesophageal Reflux Disease (GERD): GERD can cause stomach acid to flow back into the esophagus, leading to throat irritation and an increase in mucus production as a protective response.
  • Lung Cancer: In some cases, lung cancer can cause the production of phlegm, which may be blood-streaked or excessively produced.

These conditions illustrate the wide range of disorders that can lead to increased phlegm production, each with its own underlying causes and mechanisms.

The nature of the phlegm produced—such as its color, consistency, and whether it contains blood—can provide valuable clues to healthcare providers in diagnosing and treating these conditions.

Signs and Symptoms of Abnormal Phlegm

Abnormal phlegm can manifest several signs and symptoms indicative of underlying health issues, such as:

  • Color Changes: Yellow, green, brown, or red phlegm may indicate infection, inflammation, or the presence of blood.
  • Increased Volume: Producing more phlegm than usual can signal an infection or an exacerbation of a chronic respiratory condition like bronchitis or COPD.
  • Thickness or Consistency: Thick, sticky phlegm can make breathing difficult and suggest dehydration or an infection.
  • Odor: Foul-smelling phlegm could point to a bacterial infection.
  • Accompanying Symptoms: Fever, cough, shortness of breath, wheezing, or chest pain alongside abnormal phlegm production could indicate a more serious condition requiring medical attention.

Note: These symptoms help in diagnosing respiratory conditions and determining the appropriate treatment. If you experience these signs, especially in severity or persistence, seeking medical evaluation is crucial for proper care and management.

Causes of Changes in Phlegm

Changes in phlegm, including its color, consistency, and volume, can indicate a range of underlying conditions or environmental factors affecting the respiratory system:

  • Infections: Viral infections typically produce clear or white phlegm, while bacterial infections can turn it yellow, green, or brown due to the presence of immune cells.
  • Inflammation: Conditions like bronchitis, sinusitis, and allergies can increase mucus production, making it thicker due to inflammation of the airways or sinuses.
  • Irritants: Smoking and exposure to pollution or chemicals can irritate the lungs, leading to thicker and often darker phlegm as the body tries to clear the irritants.
  • Dehydration: Lack of adequate fluid intake can result in thicker phlegm, as the body doesn’t have enough water to thin the mucus.
  • Diet: Certain foods and beverages, particularly spicy or dairy products, can temporarily increase mucus production or make it seem thicker.
  • Underlying Medical Conditions: Diseases like Chronic Obstructive Pulmonary Disease (COPD), Cystic Fibrosis, and Asthma can cause the production of large amounts of thick, sticky phlegm. Gastroesophageal Reflux Disease (GERD) can also increase mucus production to protect against acid reflux.
  • Blood Presence: Finding blood in phlegm can range from being due to minor irritations like vigorous coughing to more serious conditions such as tuberculosis, lung cancer, or pulmonary embolism, changing the color to streaks of red or a rusty/dark brown.

Note: These changes in phlegm are important for diagnosis and treatment, helping healthcare providers understand the body’s response to various stimuli or conditions.

How to Get Rid of Excess Phlegm

To manage and reduce excess phlegm, you can try several strategies that focus on thinning the mucus, facilitating its expulsion, and addressing underlying causes:

  • Stay Hydrated: Drinking plenty of fluids helps thin the mucus, making it easier to cough up.
  • Humidify Your Environment: Using a humidifier adds moisture to the air, preventing mucus from becoming too thick.
  • Warm Liquids: Drinking warm teas, broths, or water can soothe the throat and thin the phlegm.
  • Steam Inhalation: Breathing in steam from a hot shower or a bowl of hot water can help loosen the mucus.
  • Saltwater Gargle: Gargling with saltwater can reduce throat irritation and help clear mucus.
  • Avoid Irritants: Smoke, dust, and chemical fumes can increase mucus production; avoiding them can help reduce phlegm.
  • Expectorants: Over-the-counter medications like guaifenesin can thin mucus, making it easier to expel.
  • Stay Upright: Being in an upright position can help prevent the accumulation of phlegm in the throat.
  • Breathing Exercises: Techniques like pursed-lip breathing can help expel mucus by improving lung function.
  • Eating Healthy: A balanced diet can support the immune system and reduce the likelihood of infections that increase phlegm production.
  • Quit Smoking: Smoking cessation is crucial as smoke irritates the airways, leading to increased mucus production.

Note: If you’re dealing with persistent or problematic phlegm, especially if accompanied by other symptoms like fever, shortness of breath, or blood in the mucus, it’s important to consult a healthcare professional to address any underlying conditions.

FAQs About Phlegm

What is the Difference Between Phlegm, Mucus, and Sputum?

Phlegm, mucus, and sputum are terms often used interchangeably but refer to slightly different substances:

  • Mucus is a slippery substance produced by mucous membranes throughout the body, including the respiratory system, to trap and eliminate irritants.
  • Phlegm specifically refers to the mucus produced by the respiratory system, especially when it’s thick and associated with an infection or disease.
  • Sputum is the term used for phlegm that is coughed up from the lungs through the mouth, often used in medical contexts to analyze respiratory health.

Should You Spit Out Phlegm?

Yes, it is generally advisable to spit out phlegm. Swallowing phlegm can reintroduce irritants, bacteria, or viruses into your system, whereas spitting it out helps remove these substances from the body.

Expelling phlegm can aid in clearing the airways, reducing congestion, and facilitating breathing.

What is Phlegm Caused By?

Phlegm is caused by various factors, including viral and bacterial infections, allergies, asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis, and gastroesophageal reflux disease (GERD).

It serves as the body’s response to inflammation or infection in the respiratory system, trapping and helping to eliminate irritants, pathogens, and debris from the airways.

Is Phlegm Good or Bad for You?

Phlegm plays a protective role in the body by trapping and helping to eliminate irritants, pathogens, and debris from the respiratory system.

While its presence can be annoying, it’s generally a sign that your body is fighting off an infection or dealing with an irritant.

However, excessive or chronic production of phlegm, especially if accompanied by other symptoms, can indicate an underlying health issue that may require medical attention.

What is the Fastest Way to Get Rid of Phlegm?

The fastest way to get rid of phlegm involves a combination of remedies:

  • Stay well-hydrated to thin the mucus, making it easier to expel.
  • Use a humidifier to moisten the air and prevent mucus from thickening.
  • Gargle with salt water to soothe the throat and loosen mucus.
  • Inhale steam from a hot shower or a bowl of hot water to help break up the phlegm.
  • Over-the-counter expectorants like guaifenesin can also thin the mucus, facilitating its removal.

How Do You Get Phlegm Out of Your Throat?

To get phlegm out of your throat:

  • Drink warm fluids like tea or broth to soothe the throat and thin the phlegm.
  • Gargle with warm salt water to help loosen mucus and reduce throat irritation.
  • Use a humidifier to add moisture to the air and prevent mucus from becoming too thick.
  • Practice controlled coughing or huff coughing techniques to help expel the phlegm more effectively.
  • Over-the-counter expectorants can also assist in thinning the phlegm, making it easier to cough up.

Is Phlegm a Sign of Recovery?

Phlegm can be a sign of recovery, especially if its color and consistency change over the course of an illness.

For instance, the transition from thick, colored phlegm to thinner, clearer phlegm may indicate that the body is successfully fighting off an infection.

However, the presence of phlegm alone isn’t always a reliable indicator of recovery, as various factors influence its production. Monitoring overall symptoms and how you feel is also crucial.

Why am I Coughing Up Phlegm but Not Sick?

Coughing up phlegm without feeling sick can result from various factors such as environmental irritants (like pollution or smoke), allergies, or post-nasal drip, where mucus from the sinuses drains into your throat, often due to allergies or sinus infections.

It’s your body’s way of clearing the airways of irritants and mucus. Dry air can also cause your throat to feel dry and produce phlegm.

However, if this condition persists, it’s wise to consult a healthcare provider for a thorough evaluation.

What Causes Brown Specks in Phlegm?

Brown specks in phlegm can be caused by a variety of factors. One common cause is smoking tobacco, which can lead to the presence of tar and other substances in the phlegm. Inhaling pollutants or dust can also result in brown specks appearing in the mucus.

Additionally, if there is bleeding in the respiratory system, even in small amounts, it can mix with phlegm and appear as brown or dark flecks.

This could be due to a respiratory infection, chronic bronchitis, or more serious conditions such as pneumonia or lung cancer.

If you consistently notice brown specks in your phlegm, it’s important to consult a healthcare provider to rule out any serious underlying conditions.

What Causes Phlegm After Eating?

Phlegm production after eating can occur for several reasons. One common cause is gastroesophageal reflux disease (GERD), where stomach acid flows back into the esophagus, leading to irritation and increased mucus production.

Certain foods and beverages, particularly spicy foods, dairy products, or allergens, can trigger mucus production in some people as part of an allergic reaction or sensitivity.

Postnasal drip, which can increase after eating, especially large meals, can also cause the sensation of phlegm accumulation.

Additionally, eating can stimulate the vagus nerve, which in turn can lead to an increase in respiratory secretions, including phlegm.

Should Phlegm Have Blood in it?

Phlegm should not normally have blood in it. The presence of blood in phlegm, known as hemoptysis, can be a sign of a more serious condition, such as a severe infection, bronchitis, pneumonia, or even a pulmonary embolism or lung cancer.

Small streaks of blood may result from prolonged coughing and is less concerning but should still be monitored.

If you notice blood in your phlegm, especially in large amounts or repeatedly, it’s important to seek medical evaluation.

Will Phlegm Go Away on Its Own?

Phlegm often goes away on its own, especially if it’s caused by a temporary condition like a cold. The body’s immune system works to fight off the infection, leading to a gradual reduction in phlegm production as you recover.

However, if phlegm persists for more than a week, worsens, or is accompanied by other symptoms like fever or difficulty breathing, it may indicate a more serious condition requiring medical attention.

In such cases, treatment may be necessary to address the underlying cause.

Final Thoughts

Phlegm is a vital component of the body’s defense system against respiratory infections and irritants.

Monitoring changes in phlegm characteristics, such as color and consistency, can aid in identifying underlying respiratory conditions and guiding appropriate treatment strategies.

By gaining a better understanding of phlegm and its associated factors, individuals can take proactive steps to maintain respiratory health and seek timely medical intervention when necessary.

John Landry, BS, RRT

Written by:

John Landry, BS, RRT

John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.


  • Shen F, Sergi C. Sputum Analysis. [Updated 2023 Feb 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024.

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