Green, yellow, or brown phlegm: What does it mean?
Last reviewed Thu 13 July 2017
By Nicole Galan
Reviewed by Stacey R. Sampson, DO
The color of phlegm can indicate if the respiratory system is healthy or not.
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.
http://www.medicalnewstoday.com/articles/318359.php
