Yes, you can give your dog Zyrtec. In fact, Zyrtec is one of the safest over-the-counter medications for dogs. It is an excellent first-aid choice and has wide safety margins – it is not likely to cause any issues even if given in large doses. Zyrtec is the brand name for the antihistamine cetirizine hydrochloride. In veterinary medicine, Zyrtec is used off-label, meaning although safe, it is not FDA approved for use in pets. However, vets support the Zyrtec use in dogs because it is beneficial, inexpensive, and readily available. Zyrtec is popularly known as an improved Benadryl version. This is because, unlike Benadryl, the active ingredient in Zyrtec (cetirizine) does not cause sedation and lethargy. This is due to the fact that cetirizine does not cross the blood-brain barrier.