Clarityn helps to reduce your allergy symptoms by stopping the effects of a substance called “histamine”, which is produced in the body when you are allergic to something. When Clarityn should be taken Clarityn relieves symptoms associated with allergic rhinitis (for example, hay fever), such as sneezing, runny or itchy nose, and burning or itchy eyes in adults and children over the age of 2 years who weigh more than 30 kg. Clarityn may also be used to help relieve symptoms of urticaria (itching, redness and number and size of hives). The effect of Clarityn will last a whole day and should help you to continue your normal daily activities and sleep