Piriton (chlorphenamine maleate) is a human antihistamine that is widely used off-label for allergic reactions in dogs. It is one of the cheapest medications used in veterinary medicine and is available over the counter without any prescription. However, it is important to understand its limitations and when it is appropriate versus when veterinary attention is needed.

Price Comparison

  • Piriton tablets (30 pack, 4mg): £3–£6 from supermarkets and pharmacies
  • Generic chlorphenamine (30 pack, 4mg): £2–£4
  • Piriton syrup (150ml): £4–£7
  • Monthly cost for a dog on twice-daily dosing: £2–£6

Piriton is one of the most affordable pet medications available. There is no price difference between buying for human or pet use — it is the same product.

What Is Piriton Used For in Dogs?

  • Insect bites and stings: Reduces swelling and itching from bee stings, wasp stings, and other insect bites
  • Mild allergic reactions: Facial swelling, hives, and itching from contact or environmental allergens
  • Vaccine reactions: Mild facial swelling after vaccinations
  • Mild seasonal allergies: May provide modest relief, though it is much less effective than Apoquel or Cytopoint for atopic dermatitis
  • Pre-medication: Sometimes given before vaccinations in dogs with a history of mild reactions

Important: Piriton is NOT effective for severe allergic reactions (anaphylaxis), which require emergency veterinary treatment with adrenaline and steroids. If your dog has difficulty breathing, collapses, or has severe swelling, go straight to the vet.

Species and Dosing

  • Dogs: Generally dosed at 0.2–0.5mg/kg twice daily. For a medium dog (10–20kg), this is typically half to one 4mg tablet twice daily
  • Cats: Chlorphenamine can be used in cats but dosing is different — always consult your vet before giving it to a cat

Critical warning: Only use plain Piriton (chlorphenamine). Do NOT use Piriteze (cetirizine), Piriton with decongestant, or any antihistamine containing pseudoephedrine or phenylephrine — these can be toxic to dogs.

Side Effects

  • Drowsiness — the most common side effect, which some owners find helpful for anxious dogs
  • Dry mouth
  • Occasional gastrointestinal upset
  • Generally very safe at recommended doses

Prescription Requirements

Piriton is a GSL (General Sales List) medicine and can be bought from any shop, supermarket, or pharmacy without a prescription. When used for your pet, technically your vet should recommend it under the prescribing cascade, but in practice many vets recommend over-the-counter purchase.

Limitations

While Piriton is cheap and widely available, it is important to understand that antihistamines are only mildly effective for most allergic skin conditions in dogs. Studies suggest antihistamines alone help only 10–30% of dogs with atopic dermatitis. For chronic skin allergies, Apoquel, Cytopoint, or Atopica are far more effective, though significantly more expensive.

Value for Money

  • Best value: Generic chlorphenamine is even cheaper than branded Piriton — identical drug
  • First-line for mild reactions: Try Piriton first for mild allergic symptoms before committing to expensive prescription medications
  • Keep a box at home: Useful for bee sting first aid while you assess whether a vet visit is needed

Last updated: March 2026. Sources: BSAVA formulary, CMA provisional decision (October 2025), VetCost data.