Cetirizine is given by mouth and is used off-label to treat and prevent pruritus (itching) associated with atopic dermatitis, urticaria (hives), and insect bite reactions in cats and dogs. Give as directed. Side effects are uncommon but may include vomiting and increased salivation. Do not use it in pets that are allergic to it or hydroxyzine. If a negative reaction occurs, contact your veterinarian.