Dog Loratadine (Clarityn) Dosage Calculator
Work out the loratadine dose for your dog by weight, in mg, 10mg tablets or syrup
Last updated: 29 October 2026
A cautious loratadine dose for dogs is 0.25–0.5 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 2.5–5 mg: up to half a 10mg Clarityn tablet, or 2.5–5 ml of the 1mg/ml syrup. 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
Loratadine is a human hayfever medicine and is not licensed for dogs in the UK, so only give it if your vet has advised it. Use plain loratadine 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
Loratadine Dose Chart for Dogs by Weight
Amount given once a day, based on 0.25–0.5 mg per kg and a maximum of 20 mg. Tablets are 10mg (Clarityn and supermarket one-a-day loratadine); syrup is Clarityn Allergy 1mg/ml.
| Dog’s weight | Dose (mg) | 10mg tablets | Syrup (1mg/ml) |
|---|---|---|---|
| 2.5 kg (6 lb) | 0.6 – 1.3 mg | Use syrup | 0.6 – 1.3 ml |
| 5 kg (11 lb) | 1.3 – 2.5 mg | Use syrup | 1.3 – 2.5 ml |
| 7.5 kg (17 lb) | 1.9 – 3.8 mg | Use syrup | 1.9 – 3.8 ml |
| 10 kg (22 lb) | 2.5 – 5 mg | ½ | 2.5 – 5 ml |
| 15 kg (33 lb) | 3.8 – 7.5 mg | ½ | 3.8 – 7.5 ml |
| 20 kg (44 lb) | 5 – 10 mg | ½ – 1 | 5 – 10 ml |
| 25 kg (55 lb) | 6.3 – 12.5 mg | 1 | 6.3 – 12.5 ml |
| 30 kg (66 lb) | 7.5 – 15 mg | 1 – 1½ | 7.5 – 15 ml |
| 40 kg (88 lb) | 10 – 20 mg | 1 – 2 | 10 – 20 ml |
Tablet column shows whole or half tablets that fall within the range. These are general guidelines, not a prescription. Veterinary references give a range of 0.25–1.1 mg per kg a day; we show the lower half to stay cautious, and your vet may advise more.
Which UK Hayfever Tablets Contain Loratadine?
Hayfever tablets with similar names can contain different drugs, so always check the active ingredient on the box.
| Product | Contains | For dogs? |
|---|---|---|
| Clarityn Allergy tablets | Loratadine 10 mg | Yes, if your vet advises it |
| Clarityn Allergy syrup | Loratadine 1 mg/ml (sweetened with maltitol, sorbitol and sucralose) | Yes, if your vet advises it |
| Supermarket "one a day" hayfever | Usually loratadine 10 mg (check the box) | Only if the box says loratadine |
| Clarinaze nasal spray | Mometasone, not loratadine | No |
| Piriteze, Zirtek, Benadryl One A Day | Cetirizine | See our cetirizine calculator |
| Benadryl Allergy Relief | Acrivastine 8 mg | No: no established dog dose |
| Any product with a decongestant (e.g. loratadine with pseudoephedrine, sold abroad) | Antihistamine plus pseudoephedrine | No: pseudoephedrine is dangerous |
Products checked October 2026. Loratadine with pseudoephedrine is not currently sold in the UK, but you may have it from abroad (for example Claritin-D from the US): never give it to a dog. For other antihistamines, see antihistamines for dogs and the cetirizine (Piriteze) calculator.
Does Loratadine Work for Dogs?
Sometimes. Vets may suggest it for mild allergies, but there is little evidence that it helps itchy skin in dogs. The MSD Veterinary Manual says second-generation antihistamines such as loratadine “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?
Loratadine vs Piriton and Piriteze
Loratadine (Clarityn), cetirizine (Piriteze) and chlorphenamine (Piriton) are three different antihistamines with three different doses, so never swap one for another at the same amount. Loratadine and cetirizine are usually given once a day and cause less drowsiness; chlorphenamine is given every 8–12 hours. Do not give two antihistamines together unless your vet has told you to. See the Piriton and cetirizine calculators, or compare them all in antihistamines for dogs.
Side Effects and When to Avoid It
Possible side effects include drowsiness (less common than with older antihistamines), dry mouth, vomiting or diarrhoea, tiredness and reduced tear production. Ask your vet before using loratadine if your dog:
- has liver disease (loratadine is broken down by the liver)
- has dry eye
- takes amiodarone, cimetidine or ketoconazole
- is pregnant, nursing or elderly
If your dog has eaten a packet, call your vet or Animal PoisonLine on 01202 509 000 with the box to hand. Too much loratadine can cause hyperactivity, drowsiness or a racing heart, and it is more urgent if the product also contains a decongestant.
Frequently Asked Questions
Can I give my dog loratadine (Clarityn)?
Vets sometimes recommend loratadine for dogs with mild allergies. It is not licensed for dogs in the UK, so only give it if your vet has advised it, and only plain loratadine with no decongestant.
How much loratadine can I give my dog?
A cautious loratadine dose for dogs is 0.25 to 0.5 mg per kg of body weight once a day, up to 20 mg. For a 10 kg dog that is 2.5 to 5 mg: up to half a 10mg Clarityn tablet, or 2.5 to 5 ml of the 1mg/ml syrup. Check the dose with your vet first.
Are hayfever tablets safe for dogs?
Only some, and only with your vet’s advice. UK hayfever tablets usually contain loratadine, cetirizine or acrivastine. Vets sometimes use loratadine or cetirizine for dogs, but never give a hayfever product that also contains a decongestant such as pseudoephedrine.
Is loratadine the same as Piriton or Piriteze?
No. Loratadine (Clarityn) is a different antihistamine from Piriton (chlorphenamine) and Piriteze (cetirizine), with a different dose. Do not swap one for another at the same amount, and do not give two antihistamines together unless your vet has told you to.
Does loratadine work for itchy dogs?
The evidence is limited. The MSD Veterinary Manual says second-generation antihistamines such as loratadine have not proved useful for controlling itching in dogs. It may help some dogs with mild allergies, but ongoing itching is usually better treated with licensed veterinary allergy medicines.
What if my dog ate a packet of loratadine tablets?
Call your vet or Animal PoisonLine (01202 509 000) for advice, with the packet to hand. Signs of too much loratadine can include hyperactivity, drowsiness or a racing heart. It is more urgent if the product also contains pseudoephedrine.