Zyrtec, also known by its generic name cetirizine, is an over-the-counter antihistamine used to treat symptoms of allergy and inflammation. Although it's a human medication, vets routinely prescribe it for animals in what's called off-label use.
How It’s Used
The recommended Zyrtec dosage for dogs is 1 mg per kg of body weight, but your vet should determine what dosage is appropriate for your pet. Veterinarians frequently recommend it to ease the immediate symptoms of stings and bites, soothe itchy skin, and treat adverse reactions to medical procedures such as blood transfusions. It's also effective against hot spots and flea and food allergies. It is sometimes given prior to vaccinations to reduce the risk of an adverse reaction. Vets sometimes give it to animals taking corticosteroids because it makes the steroids more effective, thereby lowering the required dose. It may be valuable for animals with mast cell tumors, which produce histamines that can cause inflammation.
Some forms of Zyrtec contain a decongestant, a formulation that can be toxic to dogs. It should not be administered to animals who are sensitive to it. In addition, animals who have liver or kidney problems might need their dosage adjusted to account for their condition. Vomiting and excessive salivation have been documented in some animals, as has drowsiness, primarily seen in smaller dogs. Zyrtec can skew the results of allergy testing, so ask your vet if you should discontinue the medication first.