BENYLIN® EXTRA STRENGTH MUCUS & PHLEGM PLUS COUGH CONTROL Syrup works in your lungs to break up your tough mucus and phlegm, and clear it from your chest. This EXTRA STRENGTH fast-acting syrup is specially formulated to loosen and thin out mucus and phlegm so that you can expel it when you cough. Plus, it helps silence your hacking, disruptive cough so you can get on with your day.