Phlegm is a thick, sticky substance produced by the respiratory system in response to irritation or infection. It is composed of mucus, cells, and other debris. Phlegm can be clear, white, yellow, or green, and it can vary in consistency from thin and watery to thick and sticky.
Phlegm is an important part of the body’s defense system. It helps to trap and remove foreign particles, such as bacteria and viruses, from the lungs. Phlegm also helps to keep the airways moist and lubricated.
