Green Phlegm: 9 Common Causes & What to Do

Updated in January 2023

Green phlegm is a symptom that can occur with bacterial respiratory infections, like sinustis, pneumonia or bronchitis, or COVID-19. In these cases, green phlegm is also accompanied by symptoms like a productive cough with thick mucus, sore throat, shortness of breath or fever. 

Phlegm turns green due to the presence of neutrophils in the respiratory airways. Neutrophils are defense cells produced by the immune system to destroy infections. These cells produce a green protein that is dissolved in the mucus and give it a green color. Darker or lighter green phlegm depends on the amount of protein present in the mucus. 

It is important to see a family doctor, ENT specialist or lung specialist if you notice green phlegm, so that the underlying cause can be diagnosed and interventions can be started. Treatment for bacterial infections usually involve the use of antibiotics. 

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Common causes

The most common causes of green phlegm are:

1. Sinusitis

Sinusitis is an inflammation of the nasal sinuses, which are small cavities in the skull that are located around the nose and eyes. Swelling can be caused by allergies or bacterial infections, both which usually lead to increased green phlegm. 

Generally, green phlegm will be accompanied by symptoms like nasal congestion, fever, headache, pain around the eyes and facial heaviness. 

What to do: A great way to relieve pain behind the eyes from mucus is to perform a nasal irrigation using saline solution. However, symptoms that last for over 5 days or symptoms like fever, phlegm with pus from the nose and intense facial pain should be assessed by a doctor. The doctor will likely prescribe antibiotics or nasal sprays. 

Check out natural ways to treat sinusitis using home remedies, which can be used to complement your medical treatment. 

2. Pharyngitis

Pharyngitis is an inflammation of pharynx, which is located at the back of the throat. Swelling can occur with a bacterial infection, like Streptococcus pyogenes, for example. It can lead to symptoms like sore throat, green phlegm, the sensation of phlegm stuck in the throat, difficulty swallowing, fever and a scratchy or itchy throat.

Other symptoms also include headache, general malaise and hoarseness. 

What to do: Treatment for pharyngitis varies depending on the symptoms and cause. The doctor may advise treatment with analgesics or anti-inflammatories (like acetaminophen or ibuprofen) to reduce pain, fever or throat inflammation, or antibiotics for a bacterial infection. You should also drink plenty of fluids during treatment. 

3. Infectious bronchitis 

Green phlegm can also occur with chronic infectious bronchitis. Phlegm usually starts out clear, and then becomes yellow and green as the bacterial infection worsens. 

Other common symptoms of bronchitis occur coughing with thick green phlegm that can last for up to 90 days, as well as fever, wheezing, difficulty breathing, shortness of breath and fatigue. 

What to do: You should consult a lung specialist who may prescribe medications like analgesics, anti-inflammatories, expectorant or mucolytic cough syrups, and antibiotics. Learn about other ways to get rid of phlegm at home. 

4.  Bacterial pneumonia

Bacterial pneumonia is a lung infection caused by bacteria like Streptococcus pneumoniae, Klebsiella pneumoniae or Staphylococcus aureus. It causes a productive cough with thick green mucus which may sometimes contain blood.

In addition to green phlegm, bacterial pneumonia can also lead to symptoms like fever, chiolls, chest pain or difficulty breathing. 

What to do: Treatment usually involves prescription antibiotics. The type selected by the doctor will depend on the bacteria causing the infection. 

5. Pulmonary bronchiectasis 

Yellow phlegm can also be caused by pulmonary bronchiectasis. This illness is characterized by the widening or persistent dilation of the bronchioles, as well as weakening of mucus transport systems. Both factors lead to mucus accumulation in the lungs, making the patient more prone to a bacterial infection. Read more about what different phlegm colors mean. 

One of main symptoms of bronchiectasis is thick green phlegm, although it it common to also experience symptoms like a cough with blood, shortness of breath, general malaise and chest pain. 

What to do: Treatment for pulmonary bronchiectasis should be oriented by a lung specialist. It is aimed at decreasing symptoms intensity and relieving discomfort. Treatment may involve antibiotics and bronchodilators.

6. Cystic fibrosis

Cystic fibrosis is a genetic disease that affects mucus-producing cells in the lungs. It causes an exaggerated production of sticky mucus that can accumulate in the lung and make the patient more prone to lung infections, like pneumonia. 

Common symptoms include coughing with green phlegm, fever, fatigue, and difficulty breathing. 

What to do: Treatment should be oriented by a lung specialist, who may prescribe antibiotics for the lung infection, mucolytics to thin out phlegm, and bronchodilators to open the airways and facilitate breathing.  

7. Pulmonary abscess 

Green phlegm can also occur when a pulmonary abscess ruptures. An abscess is a closed pocket that contains pus that has accumulated from a bacterial infection. Infectious can occur with Staphylococcus aureus, Klebsiella pneumoniae or Streptococcus pyogenes bacteria for example. 

A pulmonary abscess generally occurs due to a pneumonia complication that led to aspiration of food or stomach content into the lungs. It can develop into tissue necrosis in the lungs within 1 to 2 weeks if left untreated. 

What to do: Treatment for a pulmonary abscess is guided by a lung specialist, who may prescribe antibiotics, respiratory physio and, in some cases, surgical removal of affected lung tissue. 

8. COPD exacerbation

COPD, or chronic obstructive pulmonary disease, is an inflammatory lung condition that is caused by respiratory diseases, like chronic bronchitis and emphysema. This condition is associated with narrowing of the bronchi and bronchioles, which impacts airflow and breathing.

A COPD exacerbation can occur with bacterial pneumonia, and can cause symptoms like coughing with thick green phlegm, rapid breathing, shortness of breath, wheezing, fever, fatigue and swelling in the legs or ankles. 

What to do: You should complete treatment as outlined by a lung specialist, who may prescribe antibiotics, bronchodilators or corticosteroids to combat infection and relieve respiratory symptoms. 

9. Severe COVID-19 infection

A severe COVID-19 infection is characterized by symptoms that significantly impact lung function. It can lead to viral pneumonia in one or both lungs, and is more commonly seen children, older adults and people with a weakened immune system. 

In addition, COVID-19 can lead to secondary bacterial pneumonia, leading to symptoms like coughing, green phlegm and fever. It is even more common in people who are admitted to the hospital for mechanical ventilation. 

What to do: Treatment for viral pneumonia caused by COVID.19 should be administered in the hospital setting. The doctor may prescribe antivirals, like remdesivir or tocilizumab. Secondary bacterial pneumonia may be additionally treated with antibiotics. COVID-19 vaccines also play a role in preventing infections and reducing more severe symptoms. 

When to see a doctor

It is important to seek medical attention if you have green phlegm as well as: 

  • Fever
  • Chills
  • Coughing with blood
  • Productive cough
  • Difficulty breathing
  • Shortness of breath
  • Fatigue.

You should proceed immediately to the hospital if you have symptoms like low blood oxygen, chest pain, blue lips or fingers, cold sweats, pallor, rapid heart rate, chances to level of consciousness or confusion (especially in older adults).