I had radiation treatment for vocal cord cancer in 2023. For several months afterwards, mucus was a problem and I could barely speak. Believe it or not, my GP suggested I try drinking two types of herbal tea: licorice root and marshmallow root. I don’t think the licorice root did anything, but after drinking the marshmallow root tea, my voice came back within a couple of days, and the mucus began to clear up within a week.