The color of your mucus can reveal how hard your lungs are working. Yellow, green, or brown mucus often reflects accumulated debris your body is actively trying to move out. Mullein (Verbascum thapsus) has been traditionally used for respiratory support because it contains saponins and mucilage, compounds that help loosen thick mucus and support the lungs’ natural clearance process. That’s why mullein is commonly used in herbal protocols designed to help coughing feel more productive rather than