Zirtek provides 24 hour relief from hayfever and other allergy symptoms with one tablet. This medicine treats people suffering from hayfever (seasonal allergic rhinitis), perennial rhinitis (a similar condition to hayfever, caused by allergies, that continues throughout the year) and urticaria (swelling, redness and itchiness of the skin). Antihistamines like Zirtek relieve the unpleasant symptoms and discomfort associated with the above conditions, such as sneezing, itchy, runny and blocked up nose, itchy, red and watering eyes and itchy skin rashes. Most people find that their symptoms start to be relieved within half an hour of taking their tablets with the effect lasting 24 hours.