Mucus vs phlegm vs sputum overview vector

Mucus vs. Phlegm vs. Sputum: What’s the Difference? (2024)

by | Updated: May 27, 2024

In the field of respiratory care, the terms mucus, phlegm, and sputum are often used interchangeably, yet they denote distinct substances with specific roles in the human body.

Understanding the differences between these substances is crucial for diagnosing and treating respiratory conditions effectively, as their characteristics can provide valuable insights into a patient’s health status.

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

Mucus is a slippery substance produced by mucous membranes throughout the body, aiding in lubrication and protection. Phlegm, a type of mucus, is produced by the respiratory system, specifically when it’s inflamed or fighting an infection, and it often contains viruses, bacteria, and other debris. Sputum, essentially phlegm that is coughed up, can be analyzed for medical diagnosis.

While all related, their distinctions lie in their production site, composition, and role in health and disease management. 

Mucus vs. Phlegm vs. Sputum Illustration-min

Mucus vs. Phlegm vs. Sputum

Mucus, phlegm, and sputum are terms often used in discussions about respiratory health, but they have distinct meanings and implications for medical diagnosis and treatment.

Understanding these differences is essential for both healthcare professionals and patients in identifying and managing respiratory conditions.


Mucus is a viscous, slippery substance produced by the mucous membranes throughout the body, including the lungs, throat, mouth, nose, sinuses, and gastrointestinal tract.

Its primary role is to protect and moisturize the lining of these organs, trap and remove pathogens and particles like dust, pollen, and bacteria, and aid in the digestive process.

Mucus is composed of water, glycoproteins, immunoglobulins, lipids, and other substances. Its production is a normal, continuous process, essential for maintaining the health and function of mucous membranes.


Phlegm is a specific type of mucus produced by the respiratory system, especially when it is affected by disease or infection.

Unlike the thinner mucus that is continually produced to moisten and protect respiratory passages, phlegm is usually thicker and may have a color (such as yellow, green, brown, or red) indicating the presence of inflammation, bacteria, or blood.

Phlegm production increases in response to respiratory conditions like colds, flu, bronchitis, pneumonia, and chronic obstructive pulmonary disease (COPD). It serves to trap and expel the irritants and pathogens causing the respiratory issue.


Sputum is phlegm that is coughed up from the lower airways—the trachea, bronchi, and lungs. While phlegm refers to the substance itself, sputum refers to the expectorated (expelled by coughing) material.

Sputum analysis is a diagnostic tool in medicine, as its characteristics (color, consistency, and presence of cellular elements) can provide valuable information about the health of the respiratory system and the nature of respiratory diseases.

The analysis can detect bacterial infections, allergic reactions, and conditions like asthma, bronchitis, lung cancer, and tuberculosis.

Key Differences

  • Origin: Mucus is produced throughout the body by mucous membranes, while phlegm and sputum are specific to the respiratory system.
  • Function: Mucus serves a general protective and lubricating function. Phlegm traps and helps remove pathogens and irritants from the respiratory system. Sputum is phlegm that has been coughed up and can be analyzed for diagnostic purposes.
  • Context of Use: Mucus is a normal, everyday substance; phlegm is associated with illness or infection in the respiratory system; sputum is used in the context of medical analysis and diagnosis.

Note: Understanding these distinctions is crucial for accurately describing symptoms, diagnosing conditions, and targeting treatments in respiratory care.

Mucus, Phlegm, and Sputum Colors

The color of mucus, phlegm, or sputum can provide significant insights into an individual’s health, particularly regarding respiratory conditions.

The color, consistency, and even the quantity of these substances can help healthcare professionals identify the nature and severity of respiratory issues.

Here’s how different colors can matter:

Mucus Color Chart Labeled Illustration-min


Clear mucus is normal and healthy. It indicates that the body’s mucous membranes are functioning correctly, keeping the airways moist and protected from dust, allergens, and pathogens.


White phlegm can suggest the beginning of a respiratory infection, such as a common cold or viral bronchitis.

It can also indicate nasal congestion, where the mucus has become thicker and less hydrated as it drains from the sinuses.

Yellow or Green

Yellow or green phlegm is often a sign of infection, such as a bacterial or viral infection. The color comes from white blood cells, specifically neutrophils, which rush to the site of the infection.

When these cells break down, they can give the mucus a yellowish or greenish hue.

While many people associate green phlegm with a bacterial infection and the need for antibiotics, this is not always the case. Viral infections can also cause phlegm to turn green.

Brown or Black

Brown or black phlegm can be particularly concerning. It may occur in people who smoke, indicating the inhalation of tobacco smoke.

In other cases, it can suggest the presence of old blood, which may be a symptom of a more serious condition such as chronic bronchitis, pneumonia, or even lung cancer. Inhaling dirt or dust can also cause mucus to turn brown.

Red or Pink

Red or pink phlegm indicates the presence of blood. This can occur after a severe coughing episode, potentially causing small blood vessels in the airway to break.

However, it can also signal a more serious condition such as tuberculosis, pulmonary embolism, or lung cancer, especially if the bleeding is persistent or accompanied by other symptoms like weight loss or fatigue.

Note: The color of mucus, phlegm, or sputum alone is not a definitive diagnosis but rather a clue to the underlying condition. It’s important for individuals to monitor changes in the color and consistency of these substances, especially if they persist or are accompanied by other symptoms such as fever, shortness of breath, or chest pain.

How to Get Rid of Excess Mucus and Phlegm

To reduce or get rid of excess mucus and phlegm, consider the following strategies:

  • Stay Hydrated: Drinking plenty of fluids, especially water, helps thin the mucus, making it easier to expel. Warm liquids like broth, tea, or warm water with lemon can be soothing and also help break up the mucus.
  • Inhale Steam: Breathing in steam, either from a hot shower or a bowl of hot water, can help loosen the mucus and phlegm in the throat and nasal passages.
  • Use a Humidifier: A humidifier can add moisture to the air, helping to reduce mucus production and relieve congestion.
  • Saltwater Gargle: Gargling with saltwater can help clear mucus from the back of the throat and reduce phlegm.
  • Stay Away from Irritants: Smoke, perfumes, cleaning products, and other irritants can increase mucus production. Avoiding these can help reduce symptoms.
  • Use Expectorants: Over-the-counter medications like guaifenesin (e.g., Mucinex) can thin the mucus and make it easier to cough up.
  • Nasal Sprays: Saline nasal sprays can help loosen mucus in the nasal passages and clear it out. Decongestant sprays should be used cautiously and for no more than a few days.
  • Practice Good Hygiene: Washing your hands regularly and avoiding close contact with sick individuals can help prevent respiratory infections that might cause increased mucus production.
  • Eat Foods That Can Help Reduce Mucus: Some foods, like pineapple, spicy foods, and garlic, are believed to help reduce mucus production.
  • Avoid Foods That Increase Mucus Production: For some people, dairy products, refined sugars, and certain fats can increase mucus production. Reducing the intake of these foods might help.
  • Breathing Exercises: Techniques such as pursed lip breathing or diaphragmatic breathing can help clear the airways of mucus.
  • Physical Activity: Regular, moderate exercise can help improve lung function and help clear mucus.

Note: If excessive mucus or phlegm is a persistent problem or is accompanied by other symptoms like fever, shortness of breath, or chest pain, it’s advisable to consult a healthcare professional. They can determine the underlying cause and recommend appropriate treatment.

FAQs About Mucus, Phlegm, and Sputum

What is the Purpose of Mucus in the Human Body?

Mucus serves several essential functions in the human body. It acts as a protective layer, lining various organs and cavities, including the nose, throat, lungs, and digestive tract.

Mucus traps and eliminates pathogens like bacteria and viruses, dust, pollen, and other foreign particles, preventing them from entering the body and causing infection.

It also keeps these tissues moist, preventing them from drying out and becoming irritated.

Is it OK to Swallow Mucus or Phlegm?

Yes, it is generally OK to swallow mucus or phlegm. When you swallow it, the stomach acid neutralizes any potentially harmful pathogens it contains.

However, if you’re producing excessive amounts, spitting it out can sometimes feel more comfortable and can prevent stomach discomfort in some cases.

Does Phlegm Look Like Mucus?

Yes, phlegm does look like mucus, but it can have different textures and colors depending on the cause. Mucus is typically clear and thin, serving as a protective lubricant.

Phlegm, produced in the lungs and lower respiratory tract, may be thicker and can vary in color from clear to yellow, green, brown, or red, indicating different health conditions.

Is it Better to Spit Out Mucus or Swallow it?

It depends on personal comfort and the situation. Swallowing mucus is generally safe as stomach acid destroys any bacteria or viruses it may contain.

However, if you’re producing a lot of phlegm, especially if it’s thick or causing discomfort, spitting it out can be more comfortable and help you feel better.

Are Mucus and Phlegm the Same?

Mucus and phlegm are similar but not exactly the same. Mucus is a slippery substance produced by mucous membranes throughout the body, including the nose, throat, and lungs, to trap and eliminate foreign particles.

Phlegm, a type of mucus, is specifically produced in the lungs and lower respiratory tract, often in response to inflammation or disease, and can be expelled through coughing.

How Do You Know if it’s Mucus or Phlegm?

The key difference between mucus and phlegm is primarily the location within the body where it is produced and its role. Mucus is produced by mucous membranes throughout the body and serves to protect, moisturize, and filter foreign particles.

It’s typically found in the nasal passages, sinuses, and throat.

Phlegm is a type of mucus specifically produced in the lungs and lower respiratory tract, usually in response to inflammation or disease, and is often expelled through coughing. If the substance is expelled by coughing and is thicker, it’s likely to be phlegm.

What Color is Phlegm With a Chest Infection?

The color of phlegm can vary with a chest infection, often indicating the type of infection. Clear phlegm is normal, but if it turns yellow or green, it may suggest a bacterial infection.

Brown or gray phlegm could be a sign of an infection or the result of inhaling smoke or dirt. Red or pink phlegm could indicate the presence of blood, which might be due to a serious condition such as pneumonia or tuberculosis.

Note: It’s important to consult a healthcare professional if you notice changes in the color of your phlegm, especially if accompanied by other symptoms.

Why Do I Cough Up Mucus or Phlegm?

Coughing up mucus or phlegm is a natural defense mechanism for clearing the airways. Mucus production increases in response to irritants, infections, or allergies, helping to trap and eliminate these substances.

Coughing is the body’s way of expelling mucus and trapped foreign particles to keep the airways clear and prevent infection.

How Do I Know if I Have Excess Mucus?

Excess mucus can be identified by a feeling of congestion in the nasal passages or chest, a persistent need to clear the throat, coughing up phlegm, or experiencing a runny nose more frequently than usual.

Difficulty breathing, snoring, or a noticeable increase in the effort required to breathe can also be signs of excess mucus production.

What if I Have Excess Mucus When I’m Not Sick?

Excess mucus production when not sick can be caused by a variety of factors, including allergies, irritants in the air (such as smoke or pollution), dietary factors, dehydration, or certain medications.

It could also be a sign of an underlying condition that doesn’t necessarily present with the full spectrum of symptoms typically associated with being “sick,” such as chronic sinusitis or gastroesophageal reflux disease (GERD).

If excess mucus production is persistent or bothersome, consulting a healthcare provider can help identify the cause and appropriate treatment.

Where Do Mucus and Phlegm Come From?

Mucus is produced by mucous membranes which line various parts of the body such as the nose, throat, mouth, lungs, and the gastrointestinal tract. These membranes contain mucus-producing cells called goblet cells and submucosal glands that secrete mucus to trap and remove foreign particles, bacteria, and viruses.

Phlegm, a specific type of mucus, is produced in the lungs and lower respiratory tract, particularly when the body is fighting off an infection or in response to irritation. It serves to capture and clear away the irritants and pathogens from the lungs.

What’s the Difference Between Mucus and Mucous?

Mucus” refers to the thick, slippery substance produced by the mucous membranes within the body to lubricate and protect certain organs and tissues.

Mucous,” on the other hand, is an adjective used to describe something that pertains to or produces mucus, such as mucous glands or mucous membranes.

Essentially, mucus is the noun (the substance), and mucous is the adjective (describing things related to the substance).

Does the Color of My Phlegm Matter?

Yes, the color of your phlegm can provide insight into your health, particularly regarding respiratory and immune system issues. Clear phlegm is normal and indicates healthy respiratory function.

Yellow or green phlegm can suggest a bacterial or viral infection. Brown or gray phlegm might indicate the inhalation of harmful substances, like smoke or pollution. Red or pink phlegm suggests the presence of blood, which could be due to a serious condition requiring medical attention.

While the color can be a useful indicator, it’s important to consider other symptoms and consult with a healthcare professional for an accurate diagnosis.

Is Excess Phlegm a Sign of a Serious Condition?

Excess phlegm can be a sign of a serious condition, especially if accompanied by other symptoms such as fever, shortness of breath, chest pain, or blood in the phlegm.

Conditions such as bacterial pneumonia, chronic bronchitis, cystic fibrosis, and lung cancer can all lead to an increase in phlegm production.

However, excess phlegm can also result from less serious conditions like colds, allergies, or sinus infections. A healthcare provider can evaluate your symptoms and medical history to determine the cause and necessary treatment.

Final Thoughts

Distinguishing between mucus, phlegm, and sputum is more than a matter of semantics; it is vital for the accurate assessment and management of respiratory health.

Mucus serves a protective function throughout the body, while phlegm and sputum are more closely associated with the respiratory system’s response to illness or irritants.

By recognizing the nuances between these substances, healthcare professionals and patients alike can better identify the signs of respiratory conditions and take appropriate steps toward treatment and recovery.

This differentiation not only enriches our understanding of human anatomy and physiology but also enhances our ability to address and mitigate respiratory ailments with precision.

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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