Zyrtec for Dogs

Cetirizine most commonly referred to by its brand name Zyrtec is an antiallergenic used for treating allergic conditions in pets. Zyrtec is 2nd-generation histamine (H1) receptor antagonist extremely effective against pruritus (itching) resulting from urticaria, insect bites, and atopic dermatitis in dogs and cats. This antihistamine drug is also prescribed as an off-label veterinary medication for dealing with snake bites, mast cell tumor, bee stings, blood transfusion-, and vaccine reactions.

Some dog breeds like Bulldog, Golden Retriever, Dalmatian, and the Irish setter are more susceptible to allergies than other breeds. The above breeds are at greater risk of suffering from atopic dermatitis and itching caused by hives, insect bites, and other allergic conditions. Dogs experiencing the above mentioned dermal allergies get quick relief from symptoms such as chronic pruritus when administered Zyrtec tablets.    

Zyrtec at a Glance

Brand Name

Zyrtec, Aller-Tec, Reactine or Alleroff

Generic Name (active ingredient)


Drug Type

2nd-generation H1 receptor blocker, antihistamine

Is it approved by FDA?


Suitable for

Cats and dogs


Both as a prescription drug and as over-the-counter medication

Available forms

0ral suspension; chewable tablets

Is Zyrtec Safe Enough for Dogs?

Numerous researches and studies have demonstrated that dogs with allergic or atopic dermatitis tolerate and respond to Zyrtec quite well. Nevertheless, vets refrain from prescribing Zyrtec-D (an antiallergenic medication related to Zyrtec) as it contains pseudoephedrine that is harmful to dogs. Though FDA has not allowed the use of Zyrtec for animals, vets continue to prescribe the drug essentially for extra-label use. 

The Action Mechanism of Zyrtec

Histamine, a nitrogenous organic compound, is secreted by mammalians (dog is a mammal) as a response to an allergic reaction. This organic compound moves rapidly all over the body scouting for certain receptors. Once histamine tracks such receptors, the compound binds itself to them which results in sensations such as itchiness or irritation, and inflammation.

The immune system of the dog releases two distinct types of histamines-H1 and H2-that affect smooth muscles and capillaries. Attachment of histamine to H1 receptors causes fluid leakage from the capillaries leading to itching and swelling.  Additionally, the smooth muscles along the small airways become constricted that eventually causing a feeling of tightness and wheezing.

When histamine binds to H2 receptors the heart rate or pulse and secretion of gastric juices go up which enhances the risk of developing peptic or gastric ulcers. Medications that interfere with and block histamine are known as antiallergenic drugs or antihistamines, and Zyrtec is one such antihistamine. Cetirizine or Zyrtec is a special type of histamine that is very efficient in inhibiting the action of H1 receptors.

Though you can buy this antihistamine as an over-the-counter drug, you should first consult a registered veterinarian before administering the medicine to your pet.

The Right Dosage of Zyrtec for Your Dog

As stated above, you must get in touch with your vet who’ll consider all the pros and cons of Zyrtec vis-à-vis your pet before prescribing it. Ensure to rigorously abide by the course of treatment suggested by your vet as the specific dosage will be based upon the seriousness of symptoms and the dog’s weight. The typical dosage for dogs is 0.5mg/lb (1 mg/kg) depending especially on the dog’s weight and administered 1-2 times.

Zyrtec is to be given orally either as chewable tablets or in the form of an oral suspension. See to it that you complete the entire regimen of the drug until and unless the vet suggests otherwise.

Zyrtec Side Effects and Overdosing Signs

Once you start offering Zyrtec to your dog, keep your eye out for the following adverse effects:-

  • Excitability
  • Experiencing difficulty urinating (manifested by signs like bloody urine, straining to urinate, and so on)
  • Constipation
  • Vomiting
  • Salivating excessively

Zyrtec Contraindications

Your vet is unlikely to prescribe Zyrtec if your dog:-

  • Is taking psychoactive or psychotropic medications such as diazepam or Alprazolam 
  • Is hypersensitive to antihistamines
  • Is lactating or pregnant

Has a preexisting liver disease or kidney disease

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