Dog Piriton Dosage Calculator
Work out the Piriton (chlorphenamine) dose for your dog by weight, in mg, tablets or syrup
Last updated: 8 October 2026
The usual Piriton dose for dogs is 0.2–0.4 mg per kg of body weight, every 8–12 hours, up to a maximum of 8 mg (two 4mg tablets) per dose.
For example, a 10 kg dog would usually have 2–4 mg: half to one 4mg tablet, or 5–10 ml of Piriton syrup. Use the calculator for your dog’s exact weight, see the dose chart by weight, and always check with your vet first.
Important: Veterinary Consultation Required
This calculator is for informational purposes only. Always consult your vet before giving Piriton to your dog. Only use plain Piriton (chlorphenamine maleate) — never Piriteze, Benadryl, or any formulation containing decongestants like pseudoephedrine, as these can be harmful to dogs.
Calculate Dosage
Important Safety Information
- •Only use plain Piriton (chlorphenamine maleate). Never use Piriteze (cetirizine) or Benadryl: UK Benadryl products contain cetirizine or acrivastine, and some also contain the decongestant pseudoephedrine
- •Never use formulations containing decongestants such as pseudoephedrine, as these are toxic to dogs
- •Never give more than 8 mg (two 4mg tablets) in a single dose, whatever your dog’s size
- •Common side effects include drowsiness, dry mouth, and mild stomach upset
- •Watch for signs of overdose: seizures, extreme lethargy, agitation, or loss of coordination
- •Not recommended for dogs with glaucoma, urinary retention, or pregnant/nursing dogs without vet guidance
Piriton Dose Chart for Dogs by Weight
Amount per dose, given every 8–12 hours, based on 0.2–0.4 mg per kg and a maximum of 8 mg per dose. Tablets are Piriton 4mg; syrup is Piriton 2mg per 5ml.
| Dog’s weight | Dose (mg) | 4mg tablets | Syrup (2mg/5ml) |
|---|---|---|---|
| 2.5 kg (6 lb) | 0.5 – 1 mg | Use syrup | 1.3 – 2.5 ml |
| 5 kg (11 lb) | 1 – 2 mg | ½ | 2.5 – 5 ml |
| 7.5 kg (17 lb) | 1.5 – 3 mg | ½ | 3.8 – 7.5 ml |
| 10 kg (22 lb) | 2 – 4 mg | ½ – 1 | 5 – 10 ml |
| 15 kg (33 lb) | 3 – 6 mg | 1 – 1½ | 7.5 – 15 ml |
| 20 kg (44 lb) | 4 – 8 mg | 1 – 2 | 10 – 20 ml |
| 25 kg (55 lb) | 5 – 8 mg | 1½ – 2 | 12.5 – 20 ml |
| 30 kg (66 lb) | 6 – 8 mg | 1½ – 2 | 15 – 20 ml |
| 40 kg (88 lb) | 8 mg | 2 | 20 ml |
| Over 40 kg | 8 mg maximum | 2 | 20 ml |
Tablet column shows whole or half tablets that fall within the range. These are general guidelines, not a prescription. Your vet may advise a different dose for your dog.
About Piriton for Dogs
Piriton is the brand name for chlorphenamine maleate (also known as chlorpheniramine), a first-generation antihistamine that works by blocking H1 histamine receptors. It is one of the few human antihistamines that veterinarians commonly recommend for use in dogs, when given at the correct dose.
When is Piriton Prescribed for Dogs?
Veterinarians may recommend Piriton for dogs experiencing allergic reactions, insect stings or bee stings, skin allergies, atopic dermatitis, and hay fever-like symptoms. It can also be used for mild sedation before travel. It is typically used for short-term symptom relief rather than long-term treatment. If you’re not sure what’s causing the itch, see our guide: Why is my dog so itchy?
Dosage Guidelines
The usual dose of Piriton for dogs is 0.2–0.4 mg per kilogram of body weight, given every 8–12 hours, with a maximum of 8 mg (two 4mg tablets) in any single dose. Piriton is available as 4mg tablets and as a syrup containing 2mg per 5ml. The calculator converts the dose into both, so you know how many tablets or how much syrup that is.
Risks and Side Effects
The most common side effect of Piriton in dogs is drowsiness, which is expected with first-generation antihistamines. Other possible side effects include vomiting, diarrhoea, dry mouth, and urinary retention. In cases of overdose, dogs may experience seizures, severe lethargy, agitation, or coma. If you suspect your dog has taken too much Piriton, contact your vet immediately.
Piriton vs Piriteze — An Important Distinction
It is critical to understand that Piriton and Piriteze are not the same medication. Piriton contains chlorphenamine maleate, which is considered safe for dogs at the correct dose. Piriteze contains cetirizine hydrochloride, a second-generation antihistamine that is not recommended for dogs without specific veterinary instruction. Always check the active ingredient before giving any medication to your pet.
Alternatives
If your dog needs long-term allergy management, your veterinarian may recommend alternatives such as veterinary-specific antihistamines, corticosteroids, or immunotherapy. Benadryl is not a substitute: UK Benadryl products contain cetirizine or acrivastine rather than chlorphenamine, and some also contain pseudoephedrine. (Benadryl sold in the US contains diphenhydramine, a different antihistamine with a different dose.)
Frequently Asked Questions
Can I give my dog Piriton?
Yes, plain Piriton (chlorphenamine maleate) can be given to dogs under veterinary guidance at the correct dose. It is commonly used to treat allergic reactions, skin irritation, and insect stings. Always consult your vet before administering any medication.
What is the correct Piriton dosage for dogs?
The typical Piriton dose for dogs is 0.2–0.4 mg per kilogram of body weight, given every 8–12 hours, and no more than 8 mg (two 4mg tablets) per dose. For example, a 10 kg dog would usually have 2–4 mg, which is half to one 4mg tablet. Always check the dose for your dog with your vet.
Can I give my dog Piriteze instead of Piriton?
No. Piriteze contains cetirizine hydrochloride, which is a different active ingredient to Piriton (chlorphenamine maleate). Cetirizine is not recommended for dogs without specific veterinary advice. Always use plain Piriton and check the active ingredients on the box.
What should I do if my dog has an allergic reaction?
If your dog is having a severe allergic reaction (difficulty breathing, facial swelling, collapse), contact your veterinarian or emergency animal hospital immediately. Do not attempt to treat serious reactions at home. For mild reactions, your vet may advise using Piriton as a first-line treatment.
How long can my dog take Piriton?
The duration of Piriton treatment should be determined by your veterinarian. It is typically prescribed for short-term relief of allergy symptoms. Never extend treatment beyond your vet's recommendations, as prolonged use may cause side effects.