Piriteze Once A Day Allergy Syrup is used to treat the symptoms of hayfever (itchy or watery eyes, sneezing and a runny nose) and other allergies e.g. pet, house dust mite and mould spore allergies. It can also be used to relieve the rashes and itching of hives. The active ingredient is cetirizine, an antihistamine which can help to relieve the symptoms of some allergies and itchy skin rashes.