Benylin 4 Flu Liquid is a medicine used to help relieve the four main symptoms of flu: fever, body aches, nasal congestion and coughing. The ingredients it uses to do this are: paracetamol, an analgesic which helps to relieve aches and pains and fever (high temperature), diphenhydramine, an antihistamine which helps relieve coughing and dry secretions and pseudoephedrine, a decongestant which helps unblock stuffy noses.