Phlegm is the thick mucus produced deep within the lungs and lower respiratory tract. Although COVID-19 is widely recognized for causing a dry, non-productive cough, the virus can trigger phlegm production. This thick substance is the body’s natural defense mechanism, created in response to inflammation and infection within the airways. This symptom results in a wet or productive cough and helps clarify the progression of the illness.
Wet Coughs and Phlegm Prevalence in COVID-19
A cough is classified as either dry (non-productive) or wet (productive, bringing up mucus or phlegm). A dry cough remains the most common form, occurring in an estimated 50% to 70% of COVID-19 cases. However, a significant minority of patients develop a productive cough with phlegm, often around 25% of cases. This rate can reach about 35% among non-hospitalized individuals infected with variants like Omicron.
Phlegm production begins when the SARS-CoV-2 virus infects the cells lining the airways. This viral activity causes inflammation, triggering the body to generate excess mucus to trap the virus, cellular debris, and irritants. This inflammatory response leads to a buildup of thick, sticky substance in the lungs and airways. The cough reflex is then activated as the body attempts to forcefully expel this accumulated material to clear the respiratory passages.
In more severe cases, the phlegm can become abnormally thick, creating a dense, gummy material difficult to clear. This viscosity is due to components like free-floating DNA from dead lung and immune cells, along with a carbohydrate called hyaluronan. This extremely thick mucus can occlude the small airways, contributing to the breathing difficulties seen in advanced stages of the disease. The body’s hyper-inflammatory state, which includes the breakdown of cells, contributes to the altered consistency of the phlegm.
What the Color and Consistency of Phlegm Suggest
The visual characteristics of phlegm offer clues about the underlying processes in the respiratory tract. Clear or white phlegm is often considered normal, indicating routine hydration or a simple viral infection. This color suggests the mucus is primarily composed of water, salts, and immune components without a significant concentration of infection-fighting cells.
If the phlegm turns yellow or green, it signals an active immune response within the lungs. The color is derived from accumulated white blood cells, specifically neutrophils, which contain enzymes that create the greenish hue as they fight the infection. While this color suggests the presence of an infection, it does not definitively distinguish between a viral infection like COVID-19 and a bacterial co-infection.
Thin and watery consistency is generally easier to clear, but thick or sticky phlegm can indicate dehydration or a more intense inflammatory process. Phlegm tinged pink or streaked with red indicates the presence of blood. Blood in the phlegm might be caused by simple airway irritation from forceful coughing, but it can also signal a more serious underlying issue within the lungs.
Strategies for Managing Respiratory Phlegm
Managing a productive cough focuses on thinning the mucus and helping the body expel it more easily. Maintaining high fluid intake, especially warm liquids, is one of the most effective strategies. Drinking water and warm teas helps hydrate the system, which thins the phlegm and makes it less sticky.
Using a humidifier or steam inhalation helps moisturize the airways and loosen congestion. Inhaling warm, moist air thins the mucus, making it easier to cough up and clear from the chest. Controlled coughing techniques involve taking a deep breath and then exhaling with a series of short, sharp “huffs” to mobilize the phlegm without excessive strain.
Over-the-counter options can also provide relief, such as expectorants containing the ingredient guaifenesin. These medications work by loosening and thinning the mucus in the airways, promoting a more productive cough that clears the chest. While cough suppressants are generally advised for a dry cough, they should typically be avoided with a productive cough, as the goal is to clear the phlegm.
Warning Signs Requiring Medical Care
While most COVID-19 cases resolve with at-home care, certain symptoms require immediate medical attention. The most urgent sign is trouble breathing or the sudden onset of severe shortness of breath that makes it difficult to speak in full sentences. Any persistent pain or pressure felt in the chest should be considered an emergency symptom and not ignored.
Changes in mental status, such as new confusion or the inability to stay awake, are serious indicators of compromised oxygen delivery to the brain. A noticeable change in skin color, where the lips, nail beds, or skin appear pale, gray, or blue, suggests dangerously low oxygen levels in the blood. The presence of frank blood in the phlegm, causing it to look fully red or significantly pink, also warrants prompt evaluation by a healthcare professional.