Green, yellow, or brown phlegm: What does it mean?

Phlegm is a type of mucus that is produced in the lungs and nearby lower respiratory tract airways. This kind of mucus has a crucial role in preventing germs and materials from entering the airways and lungs and potentially causing an infection.

Other areas of the body, including the upper respiratory tract (nose, mouth, and throat) and gastrointestinal tract (gut) also secrete mucus.

Typically, mucus is clear and thin and not noticeable at all. When someone gets sick with a cold or an infection, the mucus can become thickened and change color.

The color of phlegm can give a lot of information about the possibility of what is going on with the lungs and other organs of the respiratory system.

Clear:
Clear mucus is normal. It consists of water, salts, antibodies and other immune system cells. After being produced in the respiratory tract, most of it goes down the back of the throat and is swallowed.

White:
White mucus signals nasal congestion. When the nasal cavity is congested, the tissues are swollen and inflamed, which slows the passage of mucus through the respiratory tract. When this happens, the mucus becomes thicker and cloudy or white.

Yellow:
Yellow mucus suggests that immune cells are starting to work at the site of the infection or another type of inflammatory insult.

White blood cells are the cells of the immune system that are responsible for fighting germs. As they continue to fight the infection, they get picked up by the mucus, giving it a yellowish tinge.

Green:
Green phlegm indicates a widespread and robust immune response. The white blood cells, germs, and other cells and proteins produced during the immune response are what give the phlegm its green color.

Red:
Red phlegm signals the presence of blood. There are many reasons for blood in the phlegm. Even just a lot of coughing, such as with a respiratory infection, can sometimes cause small blood vessels in the lungs or airways to break and bleed.

Brown:
Brown phlegm may indicate possible bleeding, and if so, is likely to be caused by bleeding that happened a while ago. Bright red or pink phlegm means the bleeding has happened more recently.

Black
Black mucus may indicate the presence of a fungal infection. Someone who has black phlegm should contact their doctor immediately, especially if they have a weakened immune system.