Use Telfast Oral Liquid For: Relief of the Symptoms of Hayfever Allergies: Sneezing, Runny and Itchy Nose, Itchy and Watery Eyes, Itchy Throat, Relief of the Symptoms of itchy skin rash/hives (Urticaria): Swelling related to allergy or hives. Itchy skin rash. Itch caused by hivesTelfast contains an active ingredient called fexofenadine hydrochloride. It is one of a group of medicines called antihistamines. Antihistamines help reduce allergic symptoms by preventing the effects of a substance called histamine, which your body produces when exposed to certain substances. Telfast is a non-sedating antihistamine which means it has been shown to not cause drowsiness.