Cetirizine (Zyrtec) Dosage Calculator
Single ingredient — cetirizine only
Allergies & Itching
Cetirizine is a second-generation antihistamine vets sometimes use off-label to ease itching from environmental allergies in dogs.
Low Drowsiness
Compared with older antihistamines like diphenhydramine (Benadryl), cetirizine tends to cause less sedation in most dogs.
Always Check the Label
Only plain, single-ingredient cetirizine is appropriate. Avoid "-D" decongestant versions and anything containing xylitol.
How to Use This Zyrtec Dosage Calculator
- 1Weigh your dog
Enter your dog's current weight and choose pounds or kilograms.
- 2Choose the reason for use
General allergies and itching are usually dosed every 12 hours; atopic dermatitis is often dosed once daily. Your vet may advise differently.
- 3Confirm the product
Select plain cetirizine. The calculator blocks Zyrtec-D (pseudoephedrine) and flags products that may contain xylitol.
- 4Read the dose, then call your vet
Use the tablet or liquid conversion shown, and confirm the final dose with your veterinarian before giving it.
Cetirizine Dosage Chart for Dogs (by Weight)
Estimated single dose at 0.5 mg per pound (1 mg/kg). General allergies are typically given twice daily; atopic dermatitis once daily. Daily totals are shown to a 20 mg/day reference ceiling.
| Dog Weight | Single Dose | 10 mg Tablets | Liquid (1 mg/mL) |
|---|---|---|---|
| 5 lb (2.3 kg) | 2.5 mg | — | 2.5 mL |
| 10 lb (4.5 kg) | 5 mg | ½ | 5 mL |
| 15 lb (6.8 kg) | 7.5 mg | 1 | 7.5 mL |
| 20 lb (9.1 kg) | 10 mg | 1 | 10 mL |
| 25 lb (11.3 kg) | 12.5 mg | 1½ | 12.5 mL |
| 30 lb (13.6 kg) | 15 mg | 1½ | 15 mL |
| 40 lb (18.1 kg) | 20 mg | 2 | 20 mL |
| 50 lb (22.7 kg) | 25 mg | 2½ | 25 mL |
| 60 lb (27.2 kg) | 30 mg | 3 | 30 mL |
| 70 lb (31.8 kg) | 35 mg | 3½ | 35 mL |
| 80 lb (36.3 kg) | 40 mg | 4 | 40 mL |
| 90 lb (40.8 kg) | 45 mg | 4½ | 45 mL |
| 100 lb (45.4 kg) | 50 mg | 5 | 50 mL |
* Educational estimate only, based on 0.5 mg/lb. Tablets shown to the nearest half. For dogs under 10 lb, use liquid for accuracy. Always confirm with your veterinarian.
Cetirizine (Zyrtec) for Dogs: What to Know
Cetirizine is the active ingredient in Zyrtec, a second-generation antihistamine. While it is an over-the-counter human medicine, veterinarians sometimes recommend it off-label to help control itching and signs of allergic skin disease in dogs. It works by blocking histamine, one of the chemicals the body releases during an allergic reaction.
A commonly cited canine dose is about 1 mg per kilogram of body weight (roughly 0.5 mg per pound), given once or twice daily depending on the condition. Cetirizine does not work for every dog, and it is not a treatment for infections, fleas, or the underlying cause of allergies. Because the right dose, frequency, and suitability depend on your dog's health, weight, and other medications, the dose your veterinarian gives you always takes priority over any estimate here.
Why vets may choose cetirizine:
- Generally well tolerated, with relatively low sedation in most dogs
- Convenient once- or twice-daily dosing
- Widely available as inexpensive generic tablets
- Can be part of a broader allergy plan alongside other treatments
Trusted sources to learn more:
Frequently Asked Questions
How much Zyrtec can I give my dog?
A commonly cited cetirizine dose for dogs is about 0.5 mg per pound of body weight (1 mg/kg). For general allergies this is often given every 12 hours, and for atopic dermatitis once daily, up to a typical reference ceiling of about 20 mg per day. For example, a 10 lb dog is roughly 5 mg and a 20 lb dog roughly 10 mg per dose. Only use plain, single-ingredient cetirizine, and confirm the exact dose with your veterinarian before giving it.
Can I give my dog Zyrtec-D?
No. Zyrtec-D contains pseudoephedrine, a decongestant that is highly toxic to dogs and can be fatal even in small amounts. Only plain cetirizine (no "-D" and no other active ingredients) is appropriate. If your dog has eaten Zyrtec-D, contact your veterinarian or the ASPCA Animal Poison Control Center (888-426-4435) immediately.
How much cetirizine for a 10, 20, or 50 lb dog?
At roughly 0.5 mg per pound: a 10 lb dog is about 5 mg per dose, a 20 lb dog about 10 mg, and a 50 lb dog about 20 mg (which may reach the daily reference ceiling). These are estimates only — large dogs may need a vet to set a higher, weight-appropriate dose. Use the calculator above for your dog's exact weight.
Can I give my dog Zyrtec every day?
Many dogs take cetirizine daily for ongoing allergies under veterinary guidance. Long-term use should be monitored by your vet, who can confirm it is appropriate for your dog and is not masking a problem that needs different treatment.
How long does cetirizine take to work in dogs?
Cetirizine is usually absorbed within a couple of hours, but for itchy skin conditions it may take a few days of consistent dosing to see the full benefit. If there is no improvement after about a week, talk to your veterinarian.
What are the side effects of cetirizine in dogs?
Cetirizine is generally well tolerated. The most common side effects are mild drowsiness, occasional vomiting, or excessive drooling. Stop the medication and contact your vet if you notice unusual lethargy, difficulty urinating, or any reaction that concerns you.
Can I give my dog children's Zyrtec liquid?
Children's liquid cetirizine (commonly 1 mg/mL) can be useful for small dogs because you can measure a precise dose. The catch is that some liquids and dissolving tablets contain xylitol, which is poisonous to dogs. Always read the inactive-ingredient list and avoid any product containing xylitol.
Is cetirizine safe for dogs?
Cetirizine is widely considered well tolerated in dogs when plain, single-ingredient product is dosed correctly under veterinary guidance, but no medication is risk-free. It is not suitable for every dog, can interact with other conditions or medicines, and the "-D" decongestant versions are dangerous. This tool cannot tell you whether it is safe for your individual dog — your veterinarian can.
My dog already swallowed Zyrtec-D or a xylitol product — what now?
Treat it as an emergency. Call your veterinarian, the nearest emergency animal hospital, or the ASPCA Animal Poison Control Center (888-426-4435) immediately, and have the packaging ready so you can report the exact ingredients and amount. Do not wait for symptoms to appear.
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Medical Disclaimer
This calculator is for general educational and informational purposes only and is not veterinary advice, diagnosis, or treatment, nor a substitute for examination by a licensed veterinarian. Cetirizine is used off-label in dogs; appropriate use depends on your individual dog. Never give Zyrtec-D (pseudoephedrine) or any product containing xylitol to your dog. Always consult your veterinarian before starting, changing, or stopping any medication. Archie Design App LLC assumes no responsibility for decisions made based on this information. In an emergency, contact your veterinarian or the ASPCA Animal Poison Control Center (888-426-4435).