Dog Cetirizine (Piriteze) Dosage Calculator
Work out the cetirizine dose for your dog by weight, in mg, 10mg tablets or children’s liquid
Last updated: 29 October 2026
The usual cetirizine dose for dogs is 0.5–1 mg per kg of body weight, once a day, up to a maximum of 20 mg.
For example, a 10 kg dog would usually have 5–10 mg: half to one 10mg Piriteze tablet, or 5–10 ml of the 1mg/ml children’s liquid. Use the calculator for your dog’s exact weight, see the dose chart by weight, and check with your vet first.
Check With Your Vet First
Cetirizine is a human medicine and is not licensed for dogs in the UK, so only give it if your vet has advised it. Use plain cetirizine only: never a product with a decongestant such as pseudoephedrine, and check liquids and melts for xylitol (E967), which is poisonous to dogs.
Calculate Dosage
Cetirizine Dose Chart for Dogs by Weight
Amount given once a day, based on 0.5–1 mg per kg and a maximum of 20 mg. Tablets are 10mg (Piriteze, Zirtek, Benadryl One A Day and supermarket cetirizine); liquid is the 1mg/ml children’s syrup or solution.
| Dog’s weight | Dose (mg) | 10mg tablets | Liquid (1mg/ml) |
|---|---|---|---|
| 2.5 kg (6 lb) | 1.3 – 2.5 mg | Use liquid | 1.3 – 2.5 ml |
| 5 kg (11 lb) | 2.5 – 5 mg | ½ | 2.5 – 5 ml |
| 7.5 kg (17 lb) | 3.8 – 7.5 mg | ½ | 3.8 – 7.5 ml |
| 10 kg (22 lb) | 5 – 10 mg | ½ – 1 | 5 – 10 ml |
| 15 kg (33 lb) | 7.5 – 15 mg | 1 – 1½ | 7.5 – 15 ml |
| 20 kg (44 lb) | 10 – 20 mg | 1 – 2 | 10 – 20 ml |
| 25 kg (55 lb) | 12.5 – 20 mg | 1½ – 2 | 12.5 – 20 ml |
| 30 kg (66 lb) | 15 – 20 mg | 1½ – 2 | 15 – 20 ml |
| 40 kg (88 lb) | 20 mg | 2 | 20 ml |
Tablet column shows whole or half tablets that fall within the range. These are general guidelines, not a prescription: some vets use a different dose or give it twice a day.
Which UK Products Contain Cetirizine?
Several brands sell the same drug, and some products with similar names contain something else. Always check the active ingredient on the box.
| Product | Contains | For dogs? |
|---|---|---|
| Piriteze Allergy tablets | Cetirizine 10 mg | Yes, if your vet advises it |
| Piriteze Allergy Relief syrup | Cetirizine 1 mg/ml (sweetened with sorbitol and saccharin) | Yes, if your vet advises it |
| Zirtek Allergy tablets and solution | Cetirizine 10 mg tablets or 1 mg/ml | Yes, if your vet advises it |
| Benadryl Allergy One A Day | Cetirizine 10 mg | Yes, if your vet advises it |
| Benadryl Allergy Children’s solution | Cetirizine 1 mg/ml | Yes, if your vet advises it |
| Supermarket "hayfever and allergy relief" | Usually cetirizine 10 mg (check the box) | Only if the box says cetirizine |
| Benadryl Allergy Relief | Acrivastine 8 mg | No: no established dog dose |
| Benadryl Allergy Relief Plus Decongestant | Acrivastine and pseudoephedrine 60 mg | No: pseudoephedrine is dangerous |
| Supermarket "one a day" hayfever | Often loratadine, not cetirizine | See our loratadine calculator |
One Benadryl Allergy Relief Plus Decongestant capsule contains 60 mg of pseudoephedrine. That is enough to cause signs such as agitation and a racing heart in dogs up to about 12 kg, and can be fatal for dogs up to about 6 kg. Products checked October 2026. For other antihistamines, see antihistamines for dogs and the loratadine (Clarityn) calculator.
Does Cetirizine Work for Dogs?
Sometimes. Vets may suggest it for hives, insect bites or mild allergies, but the evidence for itchy skin is weak. In one study cetirizine eased the itch in 18% of allergic dogs, and a later trial at a higher dose found no effect on itch from long-term skin allergy. The MSD Veterinary Manual says antihistamines like it “have not proved useful to date in controlling pruritus”.
Dogs respond differently, so a vet may try more than one antihistamine. If the itching keeps coming back, ask about licensed veterinary allergy treatments, which usually work better. Not sure what is behind it? See why is my dog so itchy?
Piriteze vs Piriton for Dogs
Piriteze (cetirizine) and Piriton (chlorphenamine) are different antihistamines with different doses, so never swap one for the other at the same amount. Cetirizine is usually given once a day and tends to cause less drowsiness. Chlorphenamine is given every 8–12 hours and is more likely to make a dog sleepy. Do not give both together unless your vet has told you to. For chlorphenamine, use the Piriton dose calculator.
Side Effects and When to Avoid It
Side effects are uncommon. The most likely are vomiting, drooling and, at higher doses, sleepiness in small dogs. Ask your vet before using cetirizine if your dog:
- has kidney or liver disease (the drug stays in the body longer)
- has seizures, glaucoma or heart disease
- has trouble passing urine or is constipated
- is pregnant, nursing or elderly
- takes sedatives, or is due an allergy skin test (stop it 2 weeks before)
Cetirizine is generally well tolerated, even in overdose. If your dog has eaten a packet, call your vet or Animal PoisonLine on 01202 509 000 with the box to hand. It is more urgent if the product also contains a decongestant or xylitol.
Frequently Asked Questions
Can I give my dog Piriteze?
Piriteze contains cetirizine, which vets sometimes recommend for dogs with allergies, hives or insect bites. It is not licensed for dogs in the UK, so only give it if your vet has advised it, and only plain cetirizine with no decongestant.
How much Piriteze can I give my dog?
The usual cetirizine dose for dogs is 0.5 to 1 mg per kg of body weight once a day, up to 20 mg. For a 10 kg dog that is 5 to 10 mg: half to one 10mg Piriteze tablet, or 5 to 10 ml of the 1mg/ml children’s liquid. Check the dose with your vet first.
Is Piriteze the same as Piriton for dogs?
No. Piriteze is cetirizine and Piriton is chlorphenamine. They are different antihistamines with different doses: cetirizine is usually given once a day, chlorphenamine every 8 to 12 hours. Do not give both together unless your vet has told you to.
Is Benadryl the same as Piriteze?
Only some of it. In the UK, Benadryl Allergy One A Day and Benadryl Allergy Children’s contain cetirizine, the same drug as Piriteze. Benadryl Allergy Relief contains acrivastine instead, and Benadryl Allergy Relief Plus Decongestant also contains pseudoephedrine, which is dangerous for dogs.
Does cetirizine work for itchy dogs?
The evidence is mixed. In one study cetirizine eased itching in 18% of allergic dogs, and another found no effect on itch from long-term skin allergy. It may help some dogs with hives, bites or mild allergies, but ongoing itching is usually better treated with licensed veterinary allergy medicines.
What if my dog ate a packet of cetirizine tablets?
Cetirizine is generally well tolerated by dogs, but call your vet or Animal PoisonLine (01202 509 000) for advice, with the packet to hand. It is more urgent if the product also contains pseudoephedrine or a sweetener such as xylitol.