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.
Note: It is extremely important NOT to use Zyrtec-D, as it contains pseudoephedrine! This ingredient is toxic to dogs. And, as with any over-the-counter (OTC) human medication, always check for xylitol (also known as birch sugar and similar names), too, as it can kill your dog.
Zyrtec Is Safe for Dogs
Zyrtec is safe for dogs, when used appropriately. Zyrtec, or cetirizine, is an oral medication available as a tablet or a liquid. While it is not required to give it with food, some dogs handle it better along with some food so there is no gastrointestinal upset. Owners generally report relief in their dog’s symptoms in about two hours.
Do not use Zyrtec in dogs with:
- Seizures
- Glaucoma
- Senior dogs
- Pregnant/nursing dogs
Important Zyrtec Drug Interactions
Avoid Zyrtec in dogs with kidney or liver disease due to interference with drug metabolism.
Cetirizine also interacts with a wide range of medications such as digoxin (for heart patients) and diazepam (Valium) and alprazolam (Xanax), which are drugs that act on the central nervous system.
Check With Your Veterinarian
With any OTC human medication, it is wise to check in with your veterinarian to be sure the drug is safe for your dog. Be sure to let your veterinarian know any medications, supplements, vitamins, etc., your dog is already taking.
The recommended dose for cetirizine (Zyrtec) is .5 mg per lb (milligrans per pound), given once a day. The standard size for human tablets is a 10 mg pill. You will need to cut a pill cutter to make sure you have the correct dose for many sizes of dogs:
| Dog Weight | Dosage | Frequency |
|---|---|---|
| 5-10 lb dog | 2.5 mg (1/4 pill) | Once a day |
| 11-25 lb dog | 5 mg (1/2 pill) | Once a day |
| 26-50 lb dog | 10 mg (1 whole pill) | Once a day |
| 51 to 75 lb dog | 15 mg (1 ½ pills) | Once a day |
| 75 lbs or more | 20 mg (2 pills) | Once a day |
Side Effects of Zyrtec in Dogs
Side effects to cetirizine (Zyrtec) are not common but could show up as gastrointestinal upset or drowsiness. Report anything unusual immediately to your veterinarian.
Zyrtec is medication used for mild symptoms such as a mild reaction to insect bites or a low-level allergy with itching. If your dog shows intense symptoms such as anaphylaxis (life-threatening shock) to a bee sting, for example, go to your veterinarian immediately.
If your dog is not showing relief to his allergy symptoms after a day or so of treatment with Zyrtec, then he needs something stronger.
Symptom Relief Only
Remember that Zyrtec relieves symptoms. It does nothing to cure the allergy itself. For that, you may need to manage the environment or consider things like desensitization.
Toxic overdosing is unusual but could occur if your dog chewed open a bottle and ingested numerous pills. Urine retention, gastrointestinal upsets, changes in heart rate and rhythm, along with exhaustion and possibly being disoriented could occur in your dog. You should contact your veterinarian and one of the animal poison control centers immediately: ASPCA Poison Control 888-426-4435; Pet Poison Helpline 855-764-7661.
I give Diana pawPrints Benedryl for seasonal allergies on vet’s recommendation. My doctor recently moved me from Benedryl to Zyrtec for my occasional symptoms. With the vet’s okay, I tried Zyrtec on Diana but it did not help her at all. The vet said this is normal as some meds work better than others on dogs. So when the trees start to pollinate, she gets the Benedryl and I take the Zyrtec, which seems to work fine on me. A bit annoying having to buy two different meds but as long as the both of us are itch-free, that’s fine.
Diana also gets baths in Chlorhexidine shampoo, sometimes once a week when it’s peak pollination. Between the shampoo and the Benedryl we have been able to manage her allergies fine.