The active ingredient is called cetirizine hydrochloride, this belongs to a family of medicines called antihistamines. Allergy & Hayfever Relief Tablets are used to treat people who have hayfever, year round allergies such as dust or pet allergies (perennial allergic rhinitis) and urticaria (swelling, redness and itchiness of the skin). Antihistamines like Allergy & Hayfever Relief Tablets relieve the unpleasant symptoms and discomfort associated with these conditions, such as sneezing, irritated, runny and blocked up nose, itchy, red and watering eyes and skin rashes.