BENYLIN® Dry Coughs Night Syrup helps to suppress the coughing mechanism, reducing the urge to cough. BENYLIN® Dry Cough Night Syrup. Helps reduce the urge to cough Provides immediate soothing relief Aids restful sleep How BENYLIN® Night Cough Syrup works: BENYLIN® Dry Coughs Night Syrup contains dextromethorphan which helps to suppress the cough mechanism. It also contains levomenthol, a decongestant which works to help relieve stuffiness in the nose to help make breathing easier. It also contains diphenhydramine which works to help relieve a runny nose.