Coughing up mucus or phlegm? Help support your recovery with Benylin, including their trusted Chesty Cough mixture. Benylin Chesty Cough uses guaifenesin to reduce and loosen the phlegm stuck to your chest, meaning that you can cough mucus up more easily and get back to feeling like you. Levomenthol included in the mixture can also help to ease congestion and clear your airways. Shop the Benylin range for the whole family, including the Infant Cough Syrup.