Mucus, a fluid in your upper respiratory system, is usually clear. But a number of health conditions can cause it to turn brown. Also known as brown phlegm or sputum, brown mucus can be due to a range of lifestyle choices, environmental factors, and health conditions.
Brown mucus is a response to irritation or inflammation in the lungs and contains dead cells, old blood, debris, tobacco tar, or air pollutants.
A range of factors and health conditions can cause brown mucus to form, including the following.
1. Smoking
When you smoke cigarettes or cigars, a sticky substance known as tar builds up in the lungs. As you cough up tar, it mixes with regular mucus, turning it brown. You can also form what’s known as a smoker’s cough, a persistent cough due to smoking, as your body works to expel the tar.
Along with brown mucus, smoking causes breathing difficulties, premature skin wrinkling, and stained teeth and skin.
2. Air Pollution and Airborne Toxins
Inhaling pollutants and toxins, like smoke and exhaust, can cause brown mucus.
Brown mucus can also develop due to inhaling certain toxins at work. For example, coal miners develop black lung (pneumoconiosis), which is a severe lung disease caused by coal dust.
3. Infections
Lung infections from bacteria and viruses cause mucus to thicken and turn brown. Some infections that cause brown mucus include:
- Bacterial bronchitis: This bacterial lung infection causes brown or yellow-green mucus. Other symptoms include chest discomfort, cough, fatigue, a mild fever, difficulty breathing, and wheezing.
- Bacterial pneumonia: This is a severe complication of a bacterial infection where tissues in the lungs become inflamed. Dark brown, yellow, or red-tinged mucus is a sign, as well as chills, fever, cough, breathing problems, night sweats, and chest pains.
- Viral infections: These are infections caused by viruses such as coronavirus, rhinovirus, and influenza (flu) viruses, which can lead to respiratory symptoms including cough, congestion, fever, fatigue, chills, and muscle aches. Brown mucus often indicates a severe infection, coupled with lung inflammation.
- Aspergillosis: This is a fungal lung infection and complication of asthma that causes wheezing attacks and difficulty breathing. In addition to breathing difficulties, chest pains, and fever, this condition causes increased production of thick, brown mucus.
4. Chronic Lung Diseases
Brown phlegm can accompany chronic (long-lasting) conditions affecting the lungs and the airways that carry air into and out of them. Chronic conditions with brown mucus as a symptom include:
- Chronic obstructive pulmonary disease (COPD): This is a set of diseases that restrict airflow, causing mucus buildup, breathing difficulties, and a chronic cough. This condition is most often linked to smoking, but can also arise due to air pollution.
- Bronchiectasis: This condition often occurs alongside an injury or other lung conditions, where the airways become damaged, widened, and scarred. Excess brown or yellow mucus is a common symptom, as well as a chronic cough, shortness of breath, wheezing, chest pain, fever, and chills.
- Cystic fibrosis: This genetic disorder, passed in families, causes an accumulation of thick, sticky mucus in the lungs, pancreas, and other parts of the body. Other symptoms include a cough, fatigue, nausea, constipation, abdominal pain, gas, and clay-colored stools.
5. Lung Abscess
Lung abscesses are pockets of pus (thick, white, or off-white fluid) that form in the tissues. They’re usually the result of an infection or injury and often form due to aspiration, inhaling bacteria or other particles from the mouth. Lung abscesses can also develop as a complication of cystic fibrosis and bronchiectasis.
In addition to brown mucus and a cough, symptoms of a lung abscess include:
6. Lung Cancer
Coughing up clear, red, pink, or brown mucus may be a sign of lung cancer. Although lung cancer is most often linked to smoking, people who don’t smoke can also develop this disease.
Other symptoms of lung cancer include:
How brown phlegm looks can vary from person to person. In general, brown mucus is thicker and darker than regular mucus. It sometimes develops a rusty tint, with the color being either uniform or having darker spots.
As brown mucus develops, it builds up in the lungs and airways and is either coughed up or blown out of the nose. With brown mucus, you will likely have a persistent productive (wet) cough, which is your body’s attempt to get rid of the excess phlegm. Sometimes, the mucus can have a strong, foul odor.
You should speak to a healthcare provider if you have symptoms like brown mucus and a cough that don’t go away or worsen.
Call your healthcare provider or seek immediate care if you experience:
- Persistent or recurring cough
- Foul-smelling, thick, yellow-green mucus
- Blood when coughing
- High fever, chills
- Low-grade fever for three or more days
- Tiredness
- Unexplained weight loss
- Shortness of breath or difficulty breathing
Healthcare providers can treat many conditions that cause brown mucus. In more severe cases, they may refer you to a pulmonologist (lung specialist) or oncologist (cancer specialist) for diagnosis or treatment.
What To Expect
Along with checking your medical history and doing a physical exam, a healthcare provider may run tests when diagnosing conditions due to brown mucus.
These tests may include:
- Lung culture sputum analysis: Clinical exam where a healthcare provider tests a sample of your mucus
- Pulse oximetry: Test that measures your blood oxygen levels
- Lung function test: Measures breathing and how well the lungs are functioning
- Sweat chloride test: Checks if you have high levels of salt in your sweat (commonly done for people who have cystic fibrosis)
- Stool samples: You collect a sample of your stool (poop) and send it for testing
- Imaging: May include chest X-ray, computerized tomography (CT) scan, and upper and lower gastrointestinal tract (GI) series scans
When you have brown mucus, the main goal is to clear it out of the body. Typically, the symptom resolves when you address the underlying cause of the issue. Home remedies are often enough for minor infections. Healthcare providers use medications and more extensive therapies for severe conditions, such as bacterial pneumonia, COPD, or lung cancer.
Home Remedies
Home remedies can manage more minor infections causing brown mucus.
You can treat brown mucus due to minor infections if you:
- Make sure you’re getting enough rest, staying home from work or school to recover
- Drink plenty of water and other fluids
- Use your inhaler if you have asthma or another lung condition
- Use a humidifier to increase moisture in the air and loosen phlegm
- Stop or avoid smoking and try to avoid second-hand smoke
Medications
Several over-the-counter and prescribed options can help relieve congestion and thick mucus.
Some options include:
- Expectorants, such as Mucinex (guaifenesin), which clear mucus from the airways
- Nasal rinses with saline solution that flush out the sinuses and break up mucus
- Decongestant medications, such as Advil (ibuprofen and pseudoephedrine) or Tylenol Sinus (acetaminophen and guaifenesin)
- Antihistamines like Claritin (loratadine) or Benadryl (diphenhydramine hydrochloride) for symptoms related to allergies
- Prescribed mucolytics—medications that thin out mucus, like Mucomyst (N-acetylcysteine) or Pulmozyme (dornase alfa)
- DNase enzyme treatment, a therapy used to break down mucus buildup
- Highly concentrated salt solutions (hypertonic saline), which are prescribed to clear mucus
Depending on the cause of brown mucus, there may be ways to prevent the condition or stop it from returning. Prevention broadly involves taking steps to protect the lungs.
You can prevent or lower your risk of brown mucus if you:
- Stop smoking and try to avoid second-hand smoke
- Wear masks to protect yourself from toxins or pollutants at work
- Try to avoid or minimize your exposure to air pollution, fumes, or exhaust
- Wash your hands regularly to prevent infection
- Eat a well-balanced diet rich in fresh fruits and vegetables, whole grains, and proteins
- Stay hydrated
- Remain physically active, as exercise can loosen mucus in the lungs
- Get enough sleep (seven to eight hours a night for adults)
- Maintain good oral hygiene
If your brown mucus is due to a more serious condition like lung infections or cystic fibrosis that is not addressed, you can develop complications, such as:
- Pneumonia: A severe complication of a bacterial or viral infection. The risk is highest for people with a weakened immune system, infants younger than 2, adults older than 65, or people who have a chronic disease like asthma. Good hygiene, keeping up with vaccinations, a healthy diet, and exercise can help prevent infections from developing into pneumonia.
- Pneumothorax: Also known as a collapsed lung, this condition occurs when the lungs can’t expand enough, which impacts the level of oxygen in the blood. People who are tall and thin are at risk for this potentially severe complication of chronic lung diseases. There’s no way to prevent pneumothorax, but avoiding smoking and getting exercise may help manage this condition.
- Respiratory failure: This is an inability of the lungs to produce enough oxygen caused by prolonged lung conditions. Quitting smoking, minimizing or avoiding alcohol intake, keeping a healthy weight, and practicing good hygiene can help prevent this severe condition.
Brown mucus is generally a sign of inflammation or infection in the lungs. Common causes of brown phlegm include smoking, exposure to toxins or pollutants in the air, cystic fibrosis, and bacterial lung infections.
Treatments for brown mucus depend on the underlying cause. They range from lifestyle changes and home remedies to over-the-counter and prescription medications.
