During a respiratory illness like COVID-19, noticing a change in the color of your phlegm can be an unexpected development. The term “Covid green” describes green-colored mucus some individuals experience, but it is a patient-generated description, not a formal medical term. This symptom can arise during various respiratory infections, leading to questions about what it signifies about the body’s response.
The Cause of Green Mucus
The appearance of green mucus is not caused by the SARS-CoV-2 virus itself, but is a direct result of the body’s immune system actively fighting an infection. When the body detects a pathogen, it dispatches immune cells to the site of the infection. Among these first responders are white blood cells known as neutrophils, which are particularly abundant.
These specialized immune cells are rich in an iron-containing enzyme called myeloperoxidase. This enzyme, which possesses a natural green color, plays a part in killing captured pathogens. As neutrophils are depleted and die off after doing their job, they break down and release their contents, including myeloperoxidase, into the surrounding mucus, which gives phlegm its color.
The intensity of the green color can deepen as the illness progresses or if an individual becomes dehydrated, as thicker mucus will appear darker. This color change can happen with either a viral or a bacterial infection. This is because neutrophils are a general defense mechanism against many types of pathogens.
Association with Secondary Infections
A primary viral infection, such as COVID-19 or influenza, can pave the way for a secondary bacterial infection. The initial virus can cause inflammation and damage to the lining of the respiratory tract. This damage weakens the protective barriers of the airways, creating an environment where bacteria can more easily cause a new infection.
The body’s immune system, already fighting the primary virus, can become overwhelmed. This makes it more difficult to fend off opportunistic bacteria. Common bacteria responsible for secondary infections include Streptococcus pneumoniae and Staphylococcus aureus, which can lead to conditions like bacterial bronchitis or pneumonia that require different medical management.
While green mucus can be present during a purely viral infection, its persistence or a sudden worsening of symptoms can suggest a secondary bacterial infection. If symptoms that were improving suddenly take a turn for the worse, it may indicate a bacterial infection has taken hold. This is a common complication in severe cases of influenza and other respiratory viral diseases.
Differentiating from Other Respiratory Conditions
Green mucus is a common symptom across a wide spectrum of respiratory illnesses and is not a definitive sign of COVID-19. Therefore, observing this symptom alone is not enough to diagnose any specific condition.
In the common cold, mucus often starts clear and may progress to yellow or green. Influenza can produce green phlegm, though it is typically accompanied by more severe symptoms like high fever and body aches. Acute bronchitis, an inflammation of the airways, is another frequent cause of green-tinged sputum. Sinusitis also commonly features thick, green nasal discharge along with facial pain and pressure.
The appearance of green mucus can be identical across these varied conditions. Distinguishing between them requires looking at the full constellation of symptoms. When necessary, specific diagnostic tests, such as a COVID-19 test, can provide a definitive diagnosis.
When to Consult a Healthcare Provider
While green mucus is often part of the natural course of a respiratory infection, its presence alongside certain other symptoms can indicate a more serious issue. The color of phlegm alone is not a cause for alarm, but you should consult a healthcare provider if specific signs are present.
You should contact a doctor if you experience green mucus accompanied by any of the following:
- Difficulty breathing or shortness of breath
- Any feeling of chest pain or pressure
- A high fever that doesn’t subside or one that returns after initially improving
- Symptoms that last for more than 10 to 14 days without any sign of improvement
- Symptoms that seem to get better only to suddenly worsen
- Coughing up phlegm that contains blood
For individuals with underlying health conditions, such as asthma, COPD, or heart disease, it is advisable to check in with a provider when respiratory symptoms develop.