Clarityn allergy 10mg 30 tablets belongs to a group of medicines known ad antihistamines antihistamines help to reduce allergic symptoms by preventing the affects of a substance called histamine which is produced in the body clarityn relieves symptoms associated with allergic rhinitis eg hay fever such as runny and itchy nose sneezing and itchy eyes clarityn tablets can also be used to relieve the symptoms of urticaria more commonly known as itching and redness from hives or nettle rash