Yes, Zyrtec (cetirizine) is generally considered safe for most dogs when used under the guidance of a veterinarian. It is an over-the-counter human medication that veterinarians commonly prescribe "off-label" for dogs to treat allergy symptoms such as itchy skin, hives, and reactions to insect stings.
Cetirizine (Zyrtec®, Reactine®) is an antihistamine used to treat and prevent pruritus (itching) associated with atopic dermatitis, urticaria (hives), and insect bite reactions in cats and dogs. It may also be used for respiratory allergy symptoms. Its use in cats and dogs is off label (extra label).
Cetirizine (Zyrtec) ¼ - ½ mg per pound (one 10mg tab per 30-40 lbs) twice daily. Loratadine (Claritin): ¼ mg per pound (half of a 10mg tablet per 20 lbs) once daily. Clemastine (Tavist-1, Antihist-1): 0.02mg per pound (one 1.34mg tablet per 65lb dog) twice daily.
You can use loratadine (Claritin) or cetirizine (Zyrtec). Zyrtec is more expensive but it seems to work better for my dog. That said they're both in the same drug class and I don't think there's any evidence of one being consistently better, either for humans or dogs.
Antihistamines. Diphenhydramine (Benadryl®), cetirizine (Zyrtec®), and loratadine (Claritin®) are commonly used antihistamines that relieve allergy symptoms or counteract allergic reactions in humans. Antihistamines are usually safe for dogs but can make some dogs drowsy and others hyperactive.
Zyrtec-D®, the combination product containing pseudoephedrine, is not safe for use in dogs or cats. Some liquid formulations of cetirizine may contain propylene glycol, which is toxic to cats. Cetirizine orally disintegrating tablets may contain xylitol, which is toxic to dogs.
ZYRTEC® tablets help relieve seasonal allergy and other upper respiratory allergy symptoms, including itchy eyes, sneezing, runny nose, itchy nose or throat, and more.
“If Zyrtec is given an appropriate dose, it can be safe for most dogs, but there are contraindications if combined with other medications,” Dr. Alleyne says.
Zyrtec has become the new first-line drug for dog allergy, largely because of its convenient dosing schedule. Although individual response to antihistamines does vary greatly, this year our clients are seeing a higher response rate than with Benedryl.
Benadryl can be used to treat itchy skin in dogs caused by skin allergies. It also reduces many of the other symptoms of allergies. However, check with your veterinarian for the correct dosage based on your dog's weight and if it might interact with other medication it is taking.
There are situations where dogs should not take Zyrtec: Dogs with kidney or liver disease: These are the organs most active in metabolizing and excreting medications.
In contrast, while Zyrtec, an antihistamine, is effective in managing mild allergies and associated symptoms, research shows that it does not offer the same rapid and reliable relief for severe cases of itchiness and skin inflammation when compared to newer medications such as Apoquel [1].
To address itchy skin on dogs, bathing one to two times week will suffice. We do not recommend over-bathing a dog with environmental allergies. And while many over-the-counter shampoos may work for your pup, we recommend dog-specific products that can be purchased from your veterinarian.
Zyrtec for Dogs. Veterinary reviewed by Michele K. Zyrtec is an over-the-counter human allergy medication sometimes given to dogs with atopic dermatitis or mild to moderate environmental allergies. Vets may recommend Zyrtec for dogs who scratch excessively, are sensitive to insect bites, or have dermatitis.
Quercetin is often considered the strongest natural antihistamine for dogs, helping to manage allergic symptoms by reducing histamine release and supporting immune function. It's a go-to option for natural allergy relief and is commonly used for seasonal allergies and itchy skin.
Usually, I will start with 5mg Zyrtec in a small dog (under 20 pounds) once a day, and 10mg Zyrtec once a day in medium-sized dogs (who weigh 20-60 pounds), and 10 mg twice a day in larger breed dogs (60+ pounds).
Since Cetirizine is a drug primarily intended for human use, and since there is no veterinarian-approved equivalent, Cetirizine for dogs and cats is considered an extra-label drug, or a drug being used outside its realm of approved use, even though it is commonly prescribed for pets by veterinarians.
Antihistamines (like Benadryl and Zyrtec) have not been shown to be highly effective at reducing itching in dogs. However, in some dogs they may result in mild improvement, or give additional benefit if used in conjunction with other treatments.
Pet MD Hydrocortisone Spray is a fast-acting formula that addresses itches, rashes, and other minor skin irritations. Safe for dogs, cats, and horses, this convenient spray targets irritated skin. Propylene Glycol USP, Hydrocortisone USP, Germaben II.
The best thing for itchy dog skin depends on the cause, but common solutions include veterinarian-prescribed treatments (medications, medicated shampoos), regular gentle bathing with soothing shampoos (like oatmeal) and conditioning, supplements (fatty acids, omega-3s), natural remedies (aloe vera), and addressing underlying issues like allergies or parasites, so a vet visit is crucial for diagnosis, notes Petbarn, the Spruce Pets, and Wedgewood Pharmacy.
Consult your veterinarian to find the food and plan best for your pet. Feed only your vet's prescription hypoallergenic food for 8 solid weeks, and nothing else. At the end of your 8 weeks, change back to your dog's normal food. If his skin gets itchy again, it's most likely your pet has food allergies.
Antihistamines like Benadryl and Zyrtec
Antihistamines, such as diphenhydramine (Benadryl® for dogs), cetirizine (Zyrtec®), and hydroxyzine, are commonly taken by humans to treat allergy symptoms. And you can use these antihistamines in most dogs as well.
Which is stronger: Zyrtec or Claritin? Zyrtec is often considered stronger and faster-acting, but it may cause more drowsiness. Claritin is less sedating and works well for mild allergies. The best choice depends on your symptoms and how your body reacts.
Other antihistamines safe for dogs
This human medication is used off-label for dogs.
If your dog reacts to a bug bite or has allergies and itches, your veterinarian may recommend Zyrtec to help make him comfortable. Zyrtec (generic name is cetirizine) is a human antihistamine drug and is used “off label” for dogs, as it is not FDA-approved for dogs.