Benylin Dual Action Dry Syrup helps to relieve dry coughs and congestion. The active ingredient dextromethorphan helps to stop persistent coughing. The syrup also contains triprolidine hydrochloride, an antihistamine which helps to relieve sneezing, runny nose, and watery eyes. Pseudoephedrine hydrochloride helps to unblock stuffy noses and relieve nasal congestion.