Mucus — that sticky, gooey substance you sometimes cough up — may be unwelcome, but it actually plays an important role in your body staying healthy.
Mucus can be found in many places throughout the body, including in the lungs, stomach, intestines, mouth and sinuses.
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"Mucus is a substance secreted by the body to provide protection and lubrication for various parts of the body," says Samuel Mathis, MD, a family medicine doctor for UTMB Health.
Think of mucus as defense for your lungs — keeping airway membranes moist and functioning properly. It also traps airborne substances like dirt, allergens and bacteria.
Coughing up mucus from the lungs, also known as phlegm or sputum, isn't a bad thing — it's a sign your body is trying to protect you, according to the National Institutes of Health (NIH).
"Most of the time mucus is clear, but it can sometimes be white as well," Dr. Mathis says. "Both clear and white mucus could be normal for some people. When mucus changes color, it can indicate something else is going on in the body."
Here, Dr. Mathis explains the reasons for coughing up white mucus and what other mucus colors mean.
If you're coughing up white phlegm but aren't sick, it could be your allergies acting up. When your nose becomes irritated and inflamed, your body produces mucus that usually drains in the back of your throat, according to the Asthma and Allergy Foundation of America (AAFA).
From there, the mucus' job is to trap potentially harmful substances like pollen, dust or bacteria, and keep it out of your lungs.
Asthma is a chronic lung condition that causes the airways to become narrow, swollen and blocked by thick phlegm, per the Cleveland Clinic.
Sometimes, asthma attacks are triggered by allergies, environmental factors, genetics or respiratory infections. Symptoms include the following, per the Cleveland Clinic:
- Tightness in your chest
- Trouble breathing
Asthma is a chronic condition that doesn't have a cure, but symptoms can be managed so they don't interfere with your daily life. If you experience these symptoms frequently, talk to your doctor, who can help you create a management plan.
3. Upper- or Lower-Respiratory Tract Infection
Thick, white phlegm is a telltale sign your body is fighting an infection, Dr. Mathis says. "The most common cause of coughing up mucus is some form of a respiratory tract infection," he says.
Upper respiratory tract infections (URI) can include sinusitis and laryngitis, while lower respiratory tract infections (LRI) include bronchitis and pneumonia.
"It's estimated that 95 to 97 percent of all URIs are caused by viral infections. The rest are from bacteria," Dr. Mathis says.
According to the Cleveland Clinic, URI symptoms include:
- Sore throat
- Runny nose
And LRI symptoms can include:
- Trouble breathing
- Chest pain
- Severe coughing
For upper-respiratory infections, Dr. Mathis recommends getting plenty of rest and fluids. "Fluids help thin out the mucus so you can cough it up or the body can clear it easier," he says.
Running a cool-mist humidifier may also be helpful, according to the Children's Hospital of Philadelphia.
Other treatments can include over-the-counter decongestants to help decrease the amount of mucus created.
If you're dealing with a bacterial infection, you'll need antibiotics to treat it.
There are certain lifestyle habits that can lead to coughing up white mucus, like becoming dehydrated. The less hydrated you are, the more thick, white mucus will build up, causing you to cough up phlegm, per the Cleveland Clinic.
Signs you're not drinking enough water include:
- Dark-colored urine
- Peeing less frequently
- Feeling tired
You can prevent dehydration by drinking plenty of water According to the U.S. National Academies of Sciences, Engineering, and Medicine, the average adult should get anywhere from 11.5 cups to 15.5 cups of water each day.
Per the Cleveland Clinic, drinking enough water will help prevent dehydration and make mucus thinner.
5. Chronic Obstructive Pulmonary Disease
Chronic obstructive pulmonary disease (COPD) is a lung disease that obstructs airflow from the lungs, per the Mayo Clinic. It's usually caused by extended exposure to gas or cigarette smoke, and it can lead to other serious conditions like lung cancer and heart disease.
A main symptom of COPD is daily coughing due to the lungs producing excess mucus. The mucus may appear white and foamy.
Other symptoms of COPD include:
- Trouble breathing
- Frequent respiratory infections
- A chronic cough
People who are frequently exposed to smoke, have a history of asthma or have underdeveloped lungs are most as risk, according to the Centers for Disease Control and Prevention (CDC). Lung function can also start to decline as people get older.
Once diagnosed by a doctor, COPD is a treatable disease. Your doctor will first recommend you stop smoking (if you're a smoker), and may prescribe inhalers, oral steroids or introduce lung therapies to manage symptoms.
6. Gastroesophageal Reflux Disease
Other common GERD symptoms include:
- Chest pain
- Trouble swallowing
- Feeling like there's a lump in your throat
According to the Mayo Clinic, risk factors for GERD include pregnancy, obesity, connective tissue disorders, smoking and taking certain medications.
Per Johns Hopkins Medicine, GERD can be treated with four different methods—lifestyle changes, medication, endoscopic therapy and surgery.
Talk to your doctor if you think you have GERD; they can determine the best treatment for you.
7. Pulmonary Edema
Pulmonary edema is a serious condition that's caused by having too much fluid in your lungs, making it hard to breathe, per the Mayo Clinic. The buildup of fluid can cause you to cough up foamy white or pink mucus.
This condition is considered a medical emergency and should be treated immediately. According to the Cleveland Clinic, signs of pulmonary edema include:
- Shortness of breath
- Coughing up blood or foamy mucus
- Wheezing and gasping for air
- Chest pain and tightness
Pulmonary edema is considered life-threatening. If you or someone you know shows signs of pulmonary edema, call 911 immediately for emergency medical help.
8. Heart Failure
A chronic cough that brings up white or pink-tinted mucus could be a sign of heart failure, according to the American Heart Association. This happens because of extra fluid that builds up in the lungs.
According to the CDC, heart failure risk factors include heart disease, diabetes, obesity, high blood pressure and certain lifestyle choices like smoking, drinking too much alcohol and not getting enough exercise.
Warning signs to look out for include:
- Shortness of breath
- Trouble breathing
- Weight gain and swelling
The best way to treat heart failure is to have it diagnosed early, per the CDC. Treatment may include medication, changing your eating and other lifestyle habits and possible surgery.
Other Mucus Colors and Their Causes
Mucus can also be other colors besides white. It's important to pay attention to your mucus color in order to understand your health.
"Just as white mucus indicates infection, the same could be said for yellow or green mucus," Dr. Mathis says. "These color changes are due to the presence of bacteria or viruses."
Other potential causes of excess mucus production or color change can also be something as simple as allergies, Dr. Mathis explains. "This typically occurs in the fall or spring when pollen counts are at their highest but can also be related to animals or other irritants."
If you're trying to determine the reason behind colorful mucus, use this phlegm color chart by The Ohio State Wexner Medical Center. Here's what some specific colors mean:
Yellow or green phlegm is usually a sign of an infection. You'll need to see your doctor to determine the exact type of infection (bacterial or viral) your body is fighting. Once diagnosed, your doctor can prescribe antibiotics for a bacterial infection or recommend you rest and hydrate to help recover from a virus.
Pink or Red Phlegm
You should tell your doctor immediately if you're coughing up pink or red mucus. It could be a sign of an infection or a serious condition like cancer or heart failure.
Grey or Black Phlegm
Dark mucus that's grey or black could be a result of working in a smoky environment or if you're a heavy smoker. Inhaling a lot of smoke can cause inflammation and produce dark-colored phlegm.
Brown mucus can come from environmental factors like breathing in dirt or coal, but it can also be a sign of chronic lung disease. The phlegm turns brown because of blood and inflammation in the lungs. This should be discussed with your doctor for diagnosis and treatment.
When to See a Doctor About Coughing Up White Mucus
Coughing is a normal response to excess mucus in the respiratory system, and it's an important reflex to get rid of allergens and pollutants from the lungs. But a persistent cough, and ongoing production of excessive mucus, should be evaluated by your doctor.
"For most people, you should consider seeing a physician if your symptoms do not improve after seven to 10 days, or if they continue to worsen over the course of a week," Dr. Mathis says.
"If you have any underlying lung conditions like asthma or COPD, you should see your doctor if symptoms do not improve within five days," he adds.
- Respiratory Care: Sputum Color: Potential Implications for Clinical Practice
- BMJ Open Respiratory Research: Sputum Colour Can Identify Patients with Neutrophilic Inflammation in Asthma
- Merck Manual: Acute Bronchitis
- Respiratory Medicine: Sputum Color as a Marker of Acute Bacterial Exacerbations of Chronic Obstructive Pulmonary Disease
- Scandanavian Journal of Primary Health Care: Sputum Colour for Diagnosis of a Bacterial Infection in Patients With Acute Cough
- Cough and Sputum Production. In: Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition;
- Asthma and Allergy Foundation of America: "Nasal Allergies (Rhinitis)"
- Cleveland Clinic: "Asthma"
- Mayo Clinic: "Dehydration"
- Centers for Disease Control and Prevention: "Chronic Obstructive Pulmonary Disease (COPD)"
- Mayo Clinic: "COPD"
- Johns Hopkins Medicine: "Gastroesophageal Reflux Disease (GERD)"
- Mayo Clinic: "Gastroesophageal reflux disease (GERD)"
- Cleveland Clinic: "Pulmonary Edema"
- Centers for Disease Control and Prevention: "Heart Failure"
- American Heart Association: "Heart Failure Signs and Symptoms"
- National Institutes of Health: "Marvels of Mucus and Phlegm"
- The Ohio State University Wexner Medical Center: "What Does the Color of Phlegm Mean?"
- Children's Hospital of Philadelphia: "Vaporizer or Humidifier: Which Is Best?"
- Harvard Health Publishing: Don't Judge Your Mucus by its Color
Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.