Benylin Chesty Coughs Non-Drowsy Benylin Chesty Coughs Non-Drowsy contains two active ingredients to help relieve chesty coughs: Guaifenesin: an expectorant which helps to loosen mucus (phlegm) from the lungs & make it easier to cough up. Levomenthol: eases congestion to help you breathe more easily. Benylin Chesty Coughs Non-Drowsy is suitable for adults & children aged 12 years & over.