Phlegm

Phlegm is a thick, slippery substance produced by the mucous membranes in our respiratory system. It plays an important role in keeping our airways moist and trapping dust, microbes, and other irritants that we breathe in. While normal amounts of phlegm are healthy and help protect our lungs, excessive production can occur during illnesses, such as colds or allergies, causing discomfort and coughing. Phlegm's color can also indicate health issues; for instance, clear phlegm is usually normal, while yellow or green may suggest an infection.