Telfast 180mg is used to relieve the symptoms of hayfever (seasonal allergic rhinitis) such as sneezing, itchy, watery or red eyes, and itchy, blocked or runny nose. Telfast 180mg is also used to relieve the symptoms of urticaria otherwise known as hives or itchy rash. It works by blocking the action of histamine which causes these unwanted effects. Telfast is a non-sedating antihistamine which means it does not make you drowsy or slow down your reactions.